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

docker-compose.dev.yml

@@ -13,7 +13,7 @@ services:
     ports:
       - "8081:8080"
     environment:
-      - DATABASE_URL=postgres://homelab:${DB_PASSWORD}@db:5432/homelab?sslmode=disable
+      - DATABASE_URL=postgres://homelab:${DB_PASSWORD}@db:5432/homelab_dev?sslmode=disable
       - JWT_SECRET=${JWT_SECRET}
       - PORT=8080
       - RESEND_API_KEY=${RESEND_API_KEY}