feat: Added more C++ and Java debug patterns + real-time lint overlay

[sreeja2007]

Description

• Added 9 new C++ debug patterns: strcpy/strcat buffer overflow, missing virtual
  destructor, reinterpret_cast, double delete, null pointer dereference, sprintf,
  catch(...), integer overflow, hardcoded file path
• Added 10 new Java debug patterns: empty catch block, printStackTrace, mutable
  static field, string concat in loop, catching Throwable, hardcoded IP,
  Thread.sleep, ignoring return value, finalize method, null pointer risk (tightened)
• Added real-time lint overlay on the code editor — red underline on error lines,
  yellow on warnings, 500ms debounce, aborts stale requests

Type of change

• New feature / enhancement

Checklist

• I have read CONTRIBUTING.md
• My branch is up to date with main
• I have not introduced duplicate issues or features
• My PR title follows the format: feat/fix/docs/test: short description
• No hardcoded secrets or API keys in my code