feat(security,quality): implement security and code quality optimizations

Phase 6: Security Optimizations
- Install DOMPurify for XSS protection
- Create sanitize utilities (HTML, input, URL, escape)
- Implement input sanitization in contact form
- Add CSRF token generation and validation
- Integrate CSRF protection in form submissions

Phase 7: Code Quality Optimizations
- Enhance TypeScript strict mode configuration
- Add noUncheckedIndexedAccess for safer array access
- Enable noImplicitReturns and noFallthroughCasesInSwitch
- Add noUnusedLocals and noUnusedParameters
- Enable exactOptionalPropertyTypes for precise types
- Configure comprehensive ESLint rules
- Add React security rules (no-unescaped-entities, jsx-no-target-blank)
- Add TypeScript best practices rules
- Add code quality rules (prefer-const, eqeqeq, curly)

Files modified:
- package.json: Add DOMPurify dependency
- src/lib/sanitize.ts: New sanitization utilities
- src/lib/csrf.ts: New CSRF protection utilities
- src/components/sections/contact-section.tsx: Security integration
- tsconfig.json: Enhanced TypeScript configuration
- eslint.config.mjs: Comprehensive ESLint rules

Impact:
- XSS attack prevention
- CSRF attack prevention
- Better type safety
- Improved code quality
- Financial-grade security standards

tsconfig.json

@@ -9,6 +9,12 @@
     "allowJs": true,
     "skipLibCheck": true,
     "strict": true,
+    "noUncheckedIndexedAccess": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "exactOptionalPropertyTypes": true,
     "noEmit": true,
     "esModuleInterop": true,
     "module": "esnext",