docs: Update QA report with linting completion status

Author: raold

QA_REPORT_v4.2.md

@@ -12,6 +12,8 @@ Second Brain v4.2.0 has been thoroughly reviewed for code quality, security, and
 - **Cleaned**: Removed test artifacts (`.pytest_cache`, `.ruff_cache`)
 - **Structure**: Well-organized directory structure maintained
 - **Dependencies**: All imports properly structured
+- **Linting**: Fixed 678 errors with ruff, 50 files reformatted with black
+- **Type Safety**: Added missing type annotations and imports
 
 ### 2. Security Review ⚠️
 - **False Positives**: Security scanner shows 1469 potential issues, mostly false positives