Restore QID propagation for chat telemetry

[shashank-kenpath]

What changed

• Generate and send one QID for each text or image chat request.
• Store the same QID on the assistant message.
• Reuse it for feedback and error telemetry.
• Preserve response-provided QIDs as an optional compatibility override.

Why

The bh-main frontend expected X-QID in the chat response, but backend PR OpenAgriNet/bharat-oan-api#137 removed that header and now uses request.qid. Feedback therefore fell back to the local message ID.

Validation

• npm run build
• eslint .
• tsc -b
• git diff --check