⚡ Bolt: Reuse requests.Session in OllamaClient

[Rohith-Shimori]

💡 What:
Refactored OllamaClient to initialize a requests.Session object in __init__ and reuse it for all API calls (generate, chat, stream).

🎯 Why:
The previous implementation created a new TCP connection (and potential SSL handshake) for every single request to the Ollama API. This adds unnecessary latency, especially for frequent or small requests.

📊 Impact:

• Reduces latency by reusing the underlying TCP connection (Keep-Alive).
• Reduces CPU overhead associated with connection setup.
• Enables connection pooling behavior.

🔬 Measurement:
Added tests/test_ollama_session.py which mocks requests.Session and verifies that session.post is called instead of requests.post. The test passes, confirming the optimization is active.

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PR created automatically by Jules for task 7054791749103307812 started by @Rohith-Shimori

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