feat: add query suggestions based on repository contents #185

[Aryanbuha890]

Summary

This PR implements contextual query suggestions based on the indexed codebase files and AST-extracted symbols, closing #185.

Changes

• Backend Symbol Caching: Updated indexer.py to write parsed functions, classes, and methods per-file directly to .index_cache.json (and maintain them in incremental re-indexing runs).
• Suggestions Endpoint: Added GET /index/suggestions in main.py which generates smart, contextual questions based on cached symbols (e.g. "How is the class SymbolExtractor implemented in symbol_parser.py?") and falls back to general queries if the cache is empty.
• Unit Tests: Added tests/test_suggestions.py to verify the endpoint correctness.
• Frontend UI & Suggestions Display:
  • Added suggestions polling in App.jsx that automatically updates the landing page when the codebase is re-indexed.
  • Rendered suggestions as modern, responsive, clickable tag buttons on startup.
  • Clicking a suggestion automatically populates the text area and submits the query.

Closes #185

[Aharshi3614]

@Aryanbuha890 Merge conflicts are there in this PR