restore rag router and groundedness response

[saurabhhhcodes]

What changed

• Re-enabled the RAG router registration so /api/v1/rag/... endpoints are exposed again.
• Switched the query endpoint to the shared RAG schema.
• Included groundedness metadata in the JSON response so the API matches the existing contract and tests.
• Added the missing module-level time import used by the RAG query path.
• Cleaned up shared frontend lint issues in the auth/API client code so the repo-wide lint job passes again.

Validation

• /Users/saurabhkumarbajpaiai/.cache/codex-runtimes/codex-primary-runtime/dependencies/python/bin/python3 -m pytest backend/tests/test_rag_ingest.py backend/tests/test_rag_query.py backend/tests/test_rag_stream.py backend/tests/integration/test_rag_feedback.py backend/tests/integration/test_rag_pipeline.py -q
• npm run lint --if-present in frontend/