Refactor Alembic configuration and update Docker setup

- Removed the `alembic.ini` file and migrated its configuration to `pyproject.toml` under `[tool.alembic]`, enhancing project organization.
- Updated the `Dockerfile` to copy `pyproject.toml` instead of `alembic.ini`, ensuring the new configuration is utilized during the build process.
- Modified `entrypoint.sh` to use the new Alembic configuration from `pyproject.toml` for database migrations.
- Updated README documentation to reflect the new Alembic configuration and usage instructions.

README.md

@@ -90,7 +90,7 @@ Ensure `.env` exists (e.g. `cp .env.example .env`) and contains `BOT_TOKEN`.
   - `services/` – Business logic (group duty pin, import); accept session from caller.
   - `utils/` – Shared date, user, and handover helpers.
   - `importers/` – Duty-schedule JSON parser.
-- `alembic/` – Migrations (use `duty_teller.config.DATABASE_URL` and `duty_teller.db.models.Base`).
+- `alembic/` – Migrations; config in `pyproject.toml` under `[tool.alembic]`; URL and metadata from `duty_teller.config` and `duty_teller.db.models.Base`. Run: `alembic -c pyproject.toml upgrade head`.
 - `webapp/` – Miniapp UI (calendar, duty list); served at `/app`.
 - `tests/` – Tests; `helpers.py` provides `make_init_data` for auth tests.
 - `pyproject.toml` – Installable package (`pip install -e .`).