fix(lint): resolve 20 gocritic, eslint, and type safety issues

Backend (Go):
- Add named return parameters for improved readability
- Modernize octal literals (0755 → 0o755, 0644 → 0o644)
- Replace nil with http.NoBody in test requests (3 instances)
- Add error handling for rows.Close() in test helper
- Close HTTP response bodies in network tests (3 instances)

Frontend (React/TypeScript):
- Add Fast Refresh export suppressions for UI components
- Replace 'any' types with proper TypeScript types (6 instances)
- Add missing useEffect dependency (calculateScore)
- Remove unused variable in Playwright test

Testing:
- Backend coverage: 87.3% (threshold: 85%)
- Frontend coverage: 87.75% (threshold: 85%)
- All tests passing with race detection
- Zero type errors

Security:
- CodeQL scans: Zero HIGH/CRITICAL findings
- Trivy scan: Zero vulnerabilities
- Pre-commit hooks: All passing

frontend/e2e/tests/security-mobile.spec.ts

@@ -286,7 +286,6 @@ test.describe('Security Dashboard Interaction Tests', () => {
 
     if (await docButton.isVisible()) {
       // Check it has correct external link behavior
-      const onclick = await docButton.getAttribute('onclick')
       const href = await docButton.getAttribute('href')
 
       // Should open external docs