feat: set timezone user level

internal/model/profile.go

@@ -6,6 +6,20 @@ type Profile struct {
 	ID        string    `db:"id"`
 	UserID    string    `db:"user_id"`
 	Name      string    `db:"name"`
+	Timezone  *string   `db:"timezone"`
 	CreatedAt time.Time `db:"created_at"`
 	UpdatedAt time.Time `db:"updated_at"`
 }
+
+// Location returns the *time.Location for this profile's timezone.
+// Returns UTC if timezone is nil or invalid.
+func (p *Profile) Location() *time.Location {
+	if p.Timezone == nil || *p.Timezone == "" {
+		return time.UTC
+	}
+	loc, err := time.LoadLocation(*p.Timezone)
+	if err != nil {
+		return time.UTC
+	}
+	return loc
+}