feat: add finance module (categories, transactions, summary, analytics)

- model/finance.go: FinanceCategory, FinanceTransaction, Summary, Analytics
- repository/finance.go: CRUD + summary/analytics queries
- service/finance.go: business logic with auto-seed default categories
- handler/finance.go: REST endpoints with owner-only check (user_id=1)
- db.go: finance_categories + finance_transactions migrations
- main.go: register /finance/* routes

Endpoints: GET/POST/PUT/DELETE /finance/categories, /finance/transactions
GET /finance/summary, /finance/analytics

cmd/api/main.go

@@ -33,6 +33,11 @@ func main() {
 		log.Fatalf("Failed to run migrations: %v", err)
 	}
 
+	// Run finance migrations
+	if err := repository.RunFinanceMigrations(db); err != nil {
+		log.Fatalf("Failed to run finance migrations: %v", err)
+	}
+
 	// Initialize repositories
 	userRepo := repository.NewUserRepository(db)
 	habitRepo := repository.NewHabitRepository(db)
@@ -40,12 +45,14 @@ func main() {
 	emailTokenRepo := repository.NewEmailTokenRepository(db)
 	habitFreezeRepo := repository.NewHabitFreezeRepository(db)
 	savingsRepo := repository.NewSavingsRepository(db)
+	financeRepo := repository.NewFinanceRepository(db)
 
 	// Initialize services
 	emailService := service.NewEmailService(cfg.ResendAPIKey, cfg.FromEmail, cfg.FromName, cfg.AppURL)
 	authService := service.NewAuthService(userRepo, emailTokenRepo, emailService, cfg.JWTSecret)
 	habitService := service.NewHabitService(habitRepo, habitFreezeRepo)
 	taskService := service.NewTaskService(taskRepo)
+	financeService := service.NewFinanceService(financeRepo)
 
 	// Initialize Telegram bot
 	telegramBot, err := bot.New(cfg.TelegramBotToken, userRepo, taskRepo, habitRepo)
@@ -72,6 +79,7 @@ func main() {
 	habitFreezeHandler := handler.NewHabitFreezeHandler(habitFreezeRepo, habitRepo)
 	savingsHandler := handler.NewSavingsHandler(savingsRepo)
 	interestHandler := handler.NewInterestHandler(db)
+	financeHandler := handler.NewFinanceHandler(financeService)
 
 	// Initialize middleware
 	authMiddleware := customMiddleware.NewAuthMiddleware(cfg.JWTSecret)
@@ -178,6 +186,20 @@ func main() {
 
 		// Savings stats
 		r.Get("/savings/stats", savingsHandler.Stats)
+
+		// Finance routes (owner-only, checked in handler)
+		r.Get("/finance/categories", financeHandler.ListCategories)
+		r.Post("/finance/categories", financeHandler.CreateCategory)
+		r.Put("/finance/categories/{id}", financeHandler.UpdateCategory)
+		r.Delete("/finance/categories/{id}", financeHandler.DeleteCategory)
+
+		r.Get("/finance/transactions", financeHandler.ListTransactions)
+		r.Post("/finance/transactions", financeHandler.CreateTransaction)
+		r.Put("/finance/transactions/{id}", financeHandler.UpdateTransaction)
+		r.Delete("/finance/transactions/{id}", financeHandler.DeleteTransaction)
+
+		r.Get("/finance/summary", financeHandler.Summary)
+		r.Get("/finance/analytics", financeHandler.Analytics)
 	})
 
 	port := os.Getenv("PORT")