Patch dockerfile and resolve StopAsyncIteration issue

[piiq]

Summary of Changes

This PR addresses critical deployment and runtime issues encountered when running the Allocator Bot in production environments, particularly after the recent toolchain modernization.

Key Fixes

🐳 Docker & Kubernetes Reliability

• Python 3.13 Migration: Updated the Dockerfile to use Python 3.13 in both builder and runtime stages.
• Explicit packaging Dependency: Added packaging>=26.0 as a direct project dependency. This resolves a ModuleNotFoundError: No module named 'packaging' that occurred in production builds (uv sync --no-dev). This issue stemmed from pypfopt (via scikit-base) requiring the module at runtime, while it was previously only available as a transitive dev dependency.

⚡️ Runtime Fixes

• Async Generator Compatibility: Replaced a generator expression in allocator_bot/api.py with an explicit async generator function. This resolves a RuntimeError: async generator raised StopAsyncIteration encountered in Python 3.13 during SSE streaming (PEP 479).

📦 Versioning

• Bump Version: Incremented project version to 0.3.1.

Verification Results

• Local Docker Build: Successfully built and verified image allocator-bot:test.
• Production Startup: Confirmed the container starts correctly, loads all modules (including pypfopt), and passes environment validation.
• Streaming Logic: Verified that real-time SSE streaming works correctly without StopAsyncIteration errors.
• Tests: All 72 unit tests are passing.