feat: Implement database configuration and migration support

- Updated `.env.example` and `purwa.toml.example` to include database URL configuration options.
- Enhanced `AppConfig` to manage database connection URLs and added a new `DatabaseSection`.
- Integrated SQLx for database operations, including migration functionalities in `purwa-orm`.
- Expanded CLI commands in `empu` for managing database migrations.
- Updated `README.md` to document new database configuration and integration test setup.
- Refined `Cargo.toml` files to include necessary dependencies for SQLx and testcontainers.

Author: HasanH47

.env.example

@@ -6,3 +6,10 @@
 
 # Example: override app display name (maps to `[app].name`)
 # PURWA_APP__NAME=my-app
+
+# Database (Sprint 4): prefer `[database].url` in purwa.toml, or either of:
+# PURWA_DATABASE__URL=postgres://postgres:postgres@127.0.0.1:5432/myapp
+# DATABASE_URL=postgres://postgres:postgres@127.0.0.1:5432/myapp
+
+# Integration tests with a real Postgres (optional if using testcontainers in CI):
+# TEST_DATABASE_URL=postgres://postgres:postgres@127.0.0.1:5432/purwa_test

.github/workflows/ci.yml

@@ -28,5 +28,6 @@ jobs:
       - name: Clippy
         run: cargo clippy --workspace -- -D warnings
 
+      # `purwa-orm` integration tests use testcontainers (Docker on the runner).
       - name: Test
         run: cargo test --workspace