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.

Dockerfile

@@ -22,7 +22,7 @@ COPY --from=builder /usr/local/bin /usr/local/bin
 
 # Application code (duty_teller package + entrypoint, migrations, webapp)
 ENV PYTHONPATH=/app
-COPY main.py alembic.ini entrypoint.sh ./
+COPY main.py pyproject.toml entrypoint.sh ./
 COPY duty_teller/ ./duty_teller/
 COPY alembic/ ./alembic/
 COPY webapp/ ./webapp/