refactor: organize type definitions into dedicated db/types/ directory

- Move type files to src/db/types/: currency_type, listing_id, user_id, money_amount, telegram_user_id
- Create types/mod.rs with proper re-exports for all type modules
- Update db/mod.rs to import from new types module instead of individual files
- All tests pass - no functionality changes
- Improves code organization by clearly separating types, DAOs, and models

Cargo.toml

@@ -10,6 +10,7 @@ sqlx = { version = "0.8.6", features = [
     "runtime-tokio-rustls",
     "sqlite",
     "chrono",
+    "macros",
     "rust_decimal",
 ] }
 rust_decimal = { version = "1.33", features = ["serde"] }