feat: add CC Switch local proxy provider

[Inference1]

Closes #403

Summary

• add a first-class CC Switch local OpenAI-compatible proxy provider
• keep the proxy token optional and never fall back to an OpenAI credential
• normalize a proxy root URL to its required /v1 endpoint and reject an explicitly cleared proxy URL
• use conservative capabilities because CC Switch can swap or fail over upstreams mid-run
• add setup documentation and provider-form coverage

Verification

• PYTHONPATH=. .venv311/bin/python -m pytest tests/test_providers.py tests/test_provider_router.py tests/test_provider_verify.py — 84 passed
• npm test -- --run src/providers/ProviderSetup.test.tsx — 4 passed
• npm run build — passed
• route-level regression coverage verifies ccswitch:<model-id> selects CC Switch and sends the proxy the bare model ID

Screenshots

Active Kimi provider in CC Switch

CC Switch local routing running

The prior OpenWorker reply screenshot has been removed from this PR description because it displayed a bare kimi-k2.7-code model and therefore did not prove the required ccswitch: route. The automated route-level regression test now verifies that path explicitly.

[Inference1]

@rohitprasad15 Would you please review this pr

[Inference1]

@psssnikhil @fahadsiddiqui Would you please review this pr