Update Dockerfile to use Python 3.13

[piiq]

This PR resolves deployment and runtime issues encountered after the Python 3.13 migration.

Key Changes:

• Python 3.13 Migration: Updated the Dockerfile to use Python 3.13 in both builder and runtime stages.
• Explicit packaging Dependency: Added packaging as a direct dependency. This resolves a ModuleNotFoundError: No module named 'packaging' encountered in production builds.
• Async Generator Fix: Replaced a generator expression in allocator_bot/api.py with an explicit async generator function. This fixes a RuntimeError: async generator raised StopAsyncIteration that occurred in Python 3.13 when handling streaming SSE responses.

Verification:

• Local Docker Build: Successfully built image allocator-bot:test.
• Runtime Test: Verified that the container starts correctly and loads all modules.
• Logic Test: Verified that the StopAsyncIteration error is resolved and streaming works correctly in Python 3.13.