feat: add indexing queue support for sequential codebase processing #181

[Aryanbuha890]

Summary

This PR implements an indexing queue system to sequentially process codebase uploads and re-indexing runs instead of rejecting concurrent requests, closing #181.

Changes

• Backend Indexing Queue:
  • Implemented indexing_queue and jobs_history in main.py.
  • Added a background worker thread (queue_worker) running sequentially. It handles temp ZIP storage using unique names (temp_upload_<job_id>.zip to prevent overwrite conflicts), path-traversal validation, file checks, and executes index_directory sequentially.
  • Handled failed jobs gracefully (logs errors, updates job status to failed, and continues to the next job in queue).
  • Exposed a GET /index/queue endpoint.
• Queue Status UI:
  • Updated SettingsPanel.jsx to poll /index/queue every 3 seconds while open.
  • Displayed a queued jobs list displaying job names and status tags (PENDING, RUNNING, COMPLETED, FAILED with error text).
• Unit Tests:
  • Updated existing tests in test_upload.py to match queueing expectations.
  • Added tests/test_queue.py verifying queue retrieval, concurrent job queueing, and graceful error handling.

Closes #181