feat: add C# detection and bug pattern support

[AnubhavC-001]

Summary

This PR adds full C# language support to the rule-based analysis engine.

Changes made

• Added C# language detection patterns to LANG_SIGNATURES
• Added 3 C#-specific bug detection patterns:
  • Empty Catch Block
  • Hardcoded Connection String
  • Thread.Sleep in Async Method
• Improved multiline regex detection in the bug analysis engine
• Refactored bug detection flow to support multiline pattern matching correctly
• Added automated backend tests for:
  • C# language detection
  • C# bug pattern detection
• Fixed rate limiting issues affecting backend test execution and CI pipelines

Challenges faced

While implementing multiline C# bug pattern detection, the existing detection engine only scanned code line-by-line using regex checks. This caused multiline patterns like empty catch blocks to fail detection during testing.

To resolve this:

• The regex matching logic was updated to analyze the full code block instead of isolated lines
• Accurate line number calculation was preserved using regex match positions
• Test failures caused by middleware rate limiting were debugged and fixed by excluding the FastAPI testclient from rate-limit checks during automated testing

All backend tests now pass successfully.

Closes #96

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor

Testing

• I ran backend tests (pytest -v)
• I tested frontend behavior manually

Checklist

• Code is readable and beginner-friendly
• No fake or placeholder behavior introduced
• Documentation updated if needed

[AnubhavC-001]

Hi @imDarshanGK , my PR #102 and PR #153 have been merged successfully. I just wanted to confirm whether the required GSSoC labels/tags have been added correctly so the contributions can reflect on the dashboard. Thank you!

[imDarshanGK]

@AnubhavC-001 Please update the PR with screenshots or implementation proof so the changes can be verified easily.
and resolve conflicts

[AnubhavC-001]

Implemented complete C# support for the QyverixAI detection engine and improved regex-based bug analysis.

Changes Made

• Added C# language detection signatures
• Added C# specific bug patterns:
  • Empty Catch Block
  • Hardcoded Connection String
  • Thread.Sleep in Async Method
• Improved multiline regex matching support in the bug detection engine
• Updated backend tests for C# detection and CI stability
• Fixed rate-limit test inconsistencies for testclient middleware bypass

Testing

• Verified all backend tests successfully
• Final test result: 53 passed

GSSoC Contributor 🚀
PR #184 FOR ISSUE #118

[AnubhavC-001]

Implemented the requested CLI improvements and updated the branch with the latest changes.

Added Features

• Added --mode support for dynamic endpoint selection (analyze, debug, suggest)
• Added --output support to save JSON analysis reports into files
• Added recursive directory analysis using --recursive
• Added handling for both single file and directory inputs
• Added directory safety validation to prevent accidental recursive scans
• Added support for analyzing multiple supported file types recursively

Testing Performed

Successfully tested:

• single file analysis
• recursive folder scanning
• debug mode execution
• JSON response output
• output file generation
• backend integration with local API server

Additional Work

• Synced branch with latest upstream changes
• Resolved rebase/update conflicts
• Verified CLI execution after branch synchronization

Requesting re-review whenever possible.

GSSoC Contributor