feat(ollama): add local Ollama model integration with admin controls, analytics, and docs

[NiladriHazra]

Ollama Integration Setup & Testing

This PR adds integration for Ollama with the local Weam backend. Follow the steps below to set up and test:

1. Install and run Ollama locally

• Default URL: http://localhost:11434/

2. Set environment variables in the Node.js service

• OLLAMA_URL (default: http://localhost:11434)
• OLLAMA_FALLBACK_ENABLED (optional)

3. Validate environment and dependencies

node validate-ollama-env.js

4. Start the Weam backend

npm run dev
# or use `npm start` depending on your setup

5. Run Ollama integration tests

node test-comprehensive-ollama.js
# optionally, if present
node test-local-ollama.js

6. Manual API smoke tests

• POST /api/ollama/chat with a short prompt to confirm responses and streaming behavior.
• GET /api/ollama/models to verify allowed models and admin settings.

Test Configuration

• Local Ollama endpoint: http://localhost:11434/ (adjust OLLAMA_URL if needed)
• Weam backend: default port 3000 (adjust as needed)
• Ensure the user account used for admin endpoints has the admin role.