Merge branch 'fix/calculation-accuracy' into main

Combines the decimal migration (int cents → decimal.Decimal via
shopspring/decimal) with main's handler refactor (split space.go into
domain handlers, WithTx/Paginate helpers, recurring deposit removal).

- Repository layer: WithTx pattern + decimal column names/types
- Handler layer: decimal arithmetic (.Sub/.Add) instead of int operators
- Models: deprecated amount_cents fields kept for SELECT * compatibility
- INSERT statements: old columns set to literal 0 for NOT NULL constraints

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/model/budget.go

@@ -3,6 +3,8 @@ package model
 import (
 	"strings"
 	"time"
+
+	"github.com/shopspring/decimal"
 )
 
 type BudgetPeriod string
@@ -22,22 +24,23 @@ const (
 )
 
 type Budget struct {
-	ID          string       `db:"id"`
-	SpaceID     string       `db:"space_id"`
-	AmountCents int          `db:"amount_cents"`
-	Period      BudgetPeriod `db:"period"`
-	StartDate   time.Time    `db:"start_date"`
-	EndDate     *time.Time   `db:"end_date"`
-	IsActive    bool         `db:"is_active"`
-	CreatedBy   string       `db:"created_by"`
-	CreatedAt   time.Time    `db:"created_at"`
-	UpdatedAt   time.Time    `db:"updated_at"`
+	ID          string          `db:"id"`
+	SpaceID     string          `db:"space_id"`
+	Amount      decimal.Decimal `db:"amount"`
+	AmountCents int             `db:"amount_cents"` // deprecated: kept for SELECT * compatibility
+	Period      BudgetPeriod    `db:"period"`
+	StartDate   time.Time       `db:"start_date"`
+	EndDate     *time.Time      `db:"end_date"`
+	IsActive    bool            `db:"is_active"`
+	CreatedBy   string          `db:"created_by"`
+	CreatedAt   time.Time       `db:"created_at"`
+	UpdatedAt   time.Time       `db:"updated_at"`
 }
 
 type BudgetWithSpent struct {
 	Budget
 	Tags       []*Tag
-	SpentCents int
+	Spent      decimal.Decimal
 	Percentage float64
 	Status     BudgetStatus
 }

internal/model/expense.go

@@ -1,6 +1,10 @@
 package model
 
-import "time"
+import (
+	"time"
+
+	"github.com/shopspring/decimal"
+)
 
 type ExpenseType string
 
@@ -10,17 +14,18 @@ const (
 )
 
 type Expense struct {
-	ID                 string      `db:"id"`
-	SpaceID            string      `db:"space_id"`
-	CreatedBy          string      `db:"created_by"`
-	Description        string      `db:"description"`
-	AmountCents        int         `db:"amount_cents"`
-	Type               ExpenseType `db:"type"`
-	Date               time.Time   `db:"date"`
-	PaymentMethodID    *string     `db:"payment_method_id"`
-	RecurringExpenseID *string     `db:"recurring_expense_id"`
-	CreatedAt          time.Time   `db:"created_at"`
-	UpdatedAt          time.Time   `db:"updated_at"`
+	ID                 string          `db:"id"`
+	SpaceID            string          `db:"space_id"`
+	CreatedBy          string          `db:"created_by"`
+	Description        string          `db:"description"`
+	Amount             decimal.Decimal `db:"amount"`
+	AmountCents        int             `db:"amount_cents"` // deprecated: kept for SELECT * compatibility
+	Type               ExpenseType     `db:"type"`
+	Date               time.Time       `db:"date"`
+	PaymentMethodID    *string         `db:"payment_method_id"`
+	RecurringExpenseID *string         `db:"recurring_expense_id"`
+	CreatedAt          time.Time       `db:"created_at"`
+	UpdatedAt          time.Time       `db:"updated_at"`
 }
 
 type ExpenseWithTags struct {
@@ -45,8 +50,8 @@ type ExpenseItem struct {
 }
 
 type TagExpenseSummary struct {
-	TagID       string  `db:"tag_id"`
-	TagName     string  `db:"tag_name"`
-	TagColor    *string `db:"tag_color"`
-	TotalAmount int     `db:"total_amount"`
+	TagID       string          `db:"tag_id"`
+	TagName     string          `db:"tag_name"`
+	TagColor    *string         `db:"tag_color"`
+	TotalAmount decimal.Decimal `db:"total_amount"`
 }

internal/model/loan.go

@@ -1,25 +1,30 @@
 package model
 
-import "time"
+import (
+	"time"
+
+	"github.com/shopspring/decimal"
+)
 
 type Loan struct {
-	ID                  string     `db:"id"`
-	SpaceID             string     `db:"space_id"`
-	Name                string     `db:"name"`
-	Description         string     `db:"description"`
-	OriginalAmountCents int        `db:"original_amount_cents"`
-	InterestRateBps     int        `db:"interest_rate_bps"`
-	StartDate           time.Time  `db:"start_date"`
-	EndDate             *time.Time `db:"end_date"`
-	IsPaidOff           bool       `db:"is_paid_off"`
-	CreatedBy           string     `db:"created_by"`
-	CreatedAt           time.Time  `db:"created_at"`
-	UpdatedAt           time.Time  `db:"updated_at"`
+	ID                  string          `db:"id"`
+	SpaceID             string          `db:"space_id"`
+	Name                string          `db:"name"`
+	Description         string          `db:"description"`
+	OriginalAmount      decimal.Decimal `db:"original_amount"`
+	OriginalAmountCents int             `db:"original_amount_cents"` // deprecated: kept for SELECT * compatibility
+	InterestRateBps     int             `db:"interest_rate_bps"`
+	StartDate           time.Time       `db:"start_date"`
+	EndDate             *time.Time      `db:"end_date"`
+	IsPaidOff           bool            `db:"is_paid_off"`
+	CreatedBy           string          `db:"created_by"`
+	CreatedAt           time.Time       `db:"created_at"`
+	UpdatedAt           time.Time       `db:"updated_at"`
 }
 
 type LoanWithPaymentSummary struct {
 	Loan
-	TotalPaidCents int
-	RemainingCents int
-	ReceiptCount   int
+	TotalPaid    decimal.Decimal
+	Remaining    decimal.Decimal
+	ReceiptCount int
 }

internal/model/money.go

@@ -0,0 +1,17 @@
+package model
+
+import (
+	"fmt"
+
+	"github.com/shopspring/decimal"
+)
+
+// FormatMoney formats a decimal as a dollar string like "$12.50"
+func FormatMoney(d decimal.Decimal) string {
+	return fmt.Sprintf("$%s", d.StringFixed(2))
+}
+
+// FormatDecimal formats a decimal for form input values like "12.50"
+func FormatDecimal(d decimal.Decimal) string {
+	return d.StringFixed(2)
+}

internal/model/money_account.go

@@ -1,6 +1,10 @@
 package model
 
-import "time"
+import (
+	"time"
+
+	"github.com/shopspring/decimal"
+)
 
 type TransferDirection string
 
@@ -21,7 +25,8 @@ type MoneyAccount struct {
 type AccountTransfer struct {
 	ID                 string            `db:"id"`
 	AccountID          string            `db:"account_id"`
-	AmountCents        int               `db:"amount_cents"`
+	Amount             decimal.Decimal   `db:"amount"`
+	AmountCents        int               `db:"amount_cents"` // deprecated: kept for SELECT * compatibility
 	Direction          TransferDirection `db:"direction"`
 	Note               string            `db:"note"`
 	RecurringDepositID *string           `db:"recurring_deposit_id"`
@@ -31,7 +36,7 @@ type AccountTransfer struct {
 
 type MoneyAccountWithBalance struct {
 	MoneyAccount
-	BalanceCents int
+	Balance decimal.Decimal
 }
 
 type AccountTransferWithAccount struct {

internal/model/receipt.go

@@ -1,6 +1,10 @@
 package model
 
-import "time"
+import (
+	"time"
+
+	"github.com/shopspring/decimal"
+)
 
 type FundingSourceType string
 
@@ -10,16 +14,17 @@ const (
 )
 
 type Receipt struct {
-	ID                 string    `db:"id"`
-	LoanID             string    `db:"loan_id"`
-	SpaceID            string    `db:"space_id"`
-	Description        string    `db:"description"`
-	TotalAmountCents   int       `db:"total_amount_cents"`
-	Date               time.Time `db:"date"`
-	RecurringReceiptID *string   `db:"recurring_receipt_id"`
-	CreatedBy          string    `db:"created_by"`
-	CreatedAt          time.Time `db:"created_at"`
-	UpdatedAt          time.Time `db:"updated_at"`
+	ID                 string          `db:"id"`
+	LoanID             string          `db:"loan_id"`
+	SpaceID            string          `db:"space_id"`
+	Description        string          `db:"description"`
+	TotalAmount        decimal.Decimal `db:"total_amount"`
+	TotalAmountCents   int             `db:"total_amount_cents"` // deprecated: kept for SELECT * compatibility
+	Date               time.Time       `db:"date"`
+	RecurringReceiptID *string         `db:"recurring_receipt_id"`
+	CreatedBy          string          `db:"created_by"`
+	CreatedAt          time.Time       `db:"created_at"`
+	UpdatedAt          time.Time       `db:"updated_at"`
 }
 
 type ReceiptFundingSource struct {
@@ -27,7 +32,8 @@ type ReceiptFundingSource struct {
 	ReceiptID        string            `db:"receipt_id"`
 	SourceType       FundingSourceType `db:"source_type"`
 	AccountID        *string           `db:"account_id"`
-	AmountCents      int               `db:"amount_cents"`
+	Amount           decimal.Decimal   `db:"amount"`
+	AmountCents      int               `db:"amount_cents"` // deprecated: kept for SELECT * compatibility
 	LinkedExpenseID  *string           `db:"linked_expense_id"`
 	LinkedTransferID *string           `db:"linked_transfer_id"`
 }

internal/model/recurring_expense.go

@@ -1,6 +1,10 @@
 package model
 
-import "time"
+import (
+	"time"
+
+	"github.com/shopspring/decimal"
+)
 
 type Frequency string
 
@@ -13,20 +17,21 @@ const (
 )
 
 type RecurringExpense struct {
-	ID              string      `db:"id"`
-	SpaceID         string      `db:"space_id"`
-	CreatedBy       string      `db:"created_by"`
-	Description     string      `db:"description"`
-	AmountCents     int         `db:"amount_cents"`
-	Type            ExpenseType `db:"type"`
-	PaymentMethodID *string     `db:"payment_method_id"`
-	Frequency       Frequency   `db:"frequency"`
-	StartDate       time.Time   `db:"start_date"`
-	EndDate         *time.Time  `db:"end_date"`
-	NextOccurrence  time.Time   `db:"next_occurrence"`
-	IsActive        bool        `db:"is_active"`
-	CreatedAt       time.Time   `db:"created_at"`
-	UpdatedAt       time.Time   `db:"updated_at"`
+	ID              string          `db:"id"`
+	SpaceID         string          `db:"space_id"`
+	CreatedBy       string          `db:"created_by"`
+	Description     string          `db:"description"`
+	Amount          decimal.Decimal `db:"amount"`
+	AmountCents     int             `db:"amount_cents"` // deprecated: kept for SELECT * compatibility
+	Type            ExpenseType     `db:"type"`
+	PaymentMethodID *string         `db:"payment_method_id"`
+	Frequency       Frequency       `db:"frequency"`
+	StartDate       time.Time       `db:"start_date"`
+	EndDate         *time.Time      `db:"end_date"`
+	NextOccurrence  time.Time       `db:"next_occurrence"`
+	IsActive        bool            `db:"is_active"`
+	CreatedAt       time.Time       `db:"created_at"`
+	UpdatedAt       time.Time       `db:"updated_at"`
 }
 
 type RecurringExpenseWithTags struct {

internal/model/recurring_receipt.go

@@ -1,21 +1,26 @@
 package model
 
-import "time"
+import (
+	"time"
+
+	"github.com/shopspring/decimal"
+)
 
 type RecurringReceipt struct {
-	ID               string     `db:"id"`
-	LoanID           string     `db:"loan_id"`
-	SpaceID          string     `db:"space_id"`
-	Description      string     `db:"description"`
-	TotalAmountCents int        `db:"total_amount_cents"`
-	Frequency        Frequency  `db:"frequency"`
-	StartDate        time.Time  `db:"start_date"`
-	EndDate          *time.Time `db:"end_date"`
-	NextOccurrence   time.Time  `db:"next_occurrence"`
-	IsActive         bool       `db:"is_active"`
-	CreatedBy        string     `db:"created_by"`
-	CreatedAt        time.Time  `db:"created_at"`
-	UpdatedAt        time.Time  `db:"updated_at"`
+	ID               string          `db:"id"`
+	LoanID           string          `db:"loan_id"`
+	SpaceID          string          `db:"space_id"`
+	Description      string          `db:"description"`
+	TotalAmount      decimal.Decimal `db:"total_amount"`
+	TotalAmountCents int             `db:"total_amount_cents"` // deprecated: kept for SELECT * compatibility
+	Frequency        Frequency       `db:"frequency"`
+	StartDate        time.Time       `db:"start_date"`
+	EndDate          *time.Time      `db:"end_date"`
+	NextOccurrence   time.Time       `db:"next_occurrence"`
+	IsActive         bool            `db:"is_active"`
+	CreatedBy        string          `db:"created_by"`
+	CreatedAt        time.Time       `db:"created_at"`
+	UpdatedAt        time.Time       `db:"updated_at"`
 }
 
 type RecurringReceiptSource struct {
@@ -23,7 +28,8 @@ type RecurringReceiptSource struct {
 	RecurringReceiptID string            `db:"recurring_receipt_id"`
 	SourceType         FundingSourceType `db:"source_type"`
 	AccountID          *string           `db:"account_id"`
-	AmountCents        int               `db:"amount_cents"`
+	Amount             decimal.Decimal   `db:"amount"`
+	AmountCents        int               `db:"amount_cents"` // deprecated: kept for SELECT * compatibility
 }
 
 type RecurringReceiptWithSources struct {

internal/model/report.go

@@ -1,15 +1,19 @@
 package model
 
-import "time"
+import (
+	"time"
+
+	"github.com/shopspring/decimal"
+)
 
 type DailySpending struct {
-	Date       time.Time `db:"date"`
-	TotalCents int       `db:"total_cents"`
+	Date  time.Time       `db:"date"`
+	Total decimal.Decimal `db:"total"`
 }
 
 type MonthlySpending struct {
-	Month      string `db:"month"`
-	TotalCents int    `db:"total_cents"`
+	Month string          `db:"month"`
+	Total decimal.Decimal `db:"total"`
 }
 
 type SpendingReport struct {
@@ -17,7 +21,7 @@ type SpendingReport struct {
 	DailySpending   []*DailySpending
 	MonthlySpending []*MonthlySpending
 	TopExpenses     []*ExpenseWithTagsAndMethod
-	TotalIncome     int
-	TotalExpenses   int
-	NetBalance      int
+	TotalIncome     decimal.Decimal
+	TotalExpenses   decimal.Decimal
+	NetBalance      decimal.Decimal
 }