Add spin session functionality and update game mechanics

- Introduced a new `spin_sessions` table to track user spin activities.
- Updated the API to include a new endpoint for spinning games, allowing users to place bets and specify spin counts.
- Enhanced game information structure and added validation for bets and spin counts.
- Implemented the `Forest Fortune` slot game mechanics, including payline evaluation and scatter functionality.
- Updated dependencies in `pyproject.toml` for development and added `httpx` for HTTP requests.
- Added unit tests for the new slot mechanics and API endpoints to ensure functionality and reliability.

README.md

@@ -28,6 +28,7 @@ API docs: http://127.0.0.1:8000/docs
 - `GET /me`, `POST /me/agreement`
 - `GET /wallet`, `POST /wallet/deposit` (amounts: 100 / 500 / 1000)
 - `GET /games`, `GET /games/{slug}`
+- `POST /games/{slug}/spin` — bet + spin_count (1…1000); Forest Fortune is playable
 
 No withdrawal endpoints by design.