update tables primary key to use serial/integer

internal/model/file.go

@@ -9,8 +9,8 @@ const (
 )
 
 type File struct {
-	ID           string    `db:"id"`
-	UserID       string    `db:"user_id"`    // Who owns/created this file
+	ID           uint64    `db:"id"`
+	UserID       uint64    `db:"user_id"`    // Who owns/created this file
 	OwnerType    string    `db:"owner_type"` // "user", "profile", etc. - the entity that owns the file
 	OwnerID      string    `db:"owner_id"`   // Polymorphic FK
 	Type         string    `db:"type"`

internal/model/profile.go

@@ -3,8 +3,8 @@ package model
 import "time"
 
 type Profile struct {
-	ID        string    `db:"id"`
-	UserID    string    `db:"user_id"`
+	ID        uint64    `db:"id"`
+	UserID    uint64    `db:"user_id"`
 	Name      string    `db:"name"`
 	CreatedAt time.Time `db:"created_at"`
 	UpdatedAt time.Time `db:"updated_at"`

internal/model/token.go

@@ -5,8 +5,8 @@ import (
 )
 
 type Token struct {
-	ID        string     `db:"id"`
-	UserID    string     `db:"user_id"`
+	ID        uint64     `db:"id"`
+	UserID    uint64     `db:"user_id"`
 	Type      string     `db:"type"` // "email_verify" or "password_reset"
 	Token     string     `db:"token"`
 	ExpiresAt time.Time  `db:"expires_at"`

internal/model/user.go

@@ -3,7 +3,7 @@ package model
 import "time"
 
 type User struct {
-	ID    string `db:"id"`
+	ID    uint64 `db:"id"`
 	Email string `db:"email"`
 	// Allow null for passwordless users
 	PasswordHash    *string    `db:"password_hash"`