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

package-lock.json

@@ -14,6 +14,7 @@
         "@types/three": "^0.183.1",
         "class-variance-authority": "^0.7.1",
         "clsx": "^2.1.1",
+        "dompurify": "^3.3.1",
         "framer-motion": "^12.34.3",
         "lucide-react": "^0.563.0",
         "next": "16.1.6",
@@ -25,6 +26,7 @@
       },
       "devDependencies": {
         "@tailwindcss/postcss": "^4",
+        "@types/dompurify": "^3.0.5",
         "@types/node": "^20",
         "@types/react": "^19",
         "@types/react-dom": "^19",
@@ -2527,6 +2529,16 @@
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       "license": "MIT"
     },
+    "node_modules/@types/dompurify": {
+      "version": "3.0.5",
+      "resolved": "https://registry.npmjs.org/@types/dompurify/-/dompurify-3.0.5.tgz",
+      "integrity": "sha512-1Wg0g3BtQF7sSb27fJQAKck1HECM6zV1EB66j8JH9i3LCjYabJa0FSdiSgsD5K/RbrsR0SiraKacLB+T8ZVYAg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/trusted-types": "*"
+      }
+    },
     "node_modules/@types/estree": {
       "version": "1.0.8",
       "resolved": "https://registry.npmjs.org/@types/estree/-/estree-1.0.8.tgz",
@@ -2605,6 +2617,13 @@
         "meshoptimizer": "~1.0.1"
       }
     },
+    "node_modules/@types/trusted-types": {
+      "version": "2.0.7",
+      "resolved": "https://registry.npmjs.org/@types/trusted-types/-/trusted-types-2.0.7.tgz",
+      "integrity": "sha512-ScaPdn1dQczgbl0QFTeTOmVHFULt394XJgOQNoyVhZ6r2vLnMLJfBPd53SB52T/3G36VI1/g2MZaX0cwDuXsfw==",
+      "devOptional": true,
+      "license": "MIT"
+    },
     "node_modules/@types/webxr": {
       "version": "0.5.24",
       "resolved": "https://registry.npmjs.org/@types/webxr/-/webxr-0.5.24.tgz",
@@ -4181,6 +4200,15 @@
         "node": ">=0.10.0"
       }
     },
+    "node_modules/dompurify": {
+      "version": "3.3.1",
+      "resolved": "https://registry.npmjs.org/dompurify/-/dompurify-3.3.1.tgz",
+      "integrity": "sha512-qkdCKzLNtrgPFP1Vo+98FRzJnBRGe4ffyCea9IwHB1fyxPOeNTHpLKYGd4Uk9xvNoH0ZoOjwZxNptyMwqrId1Q==",
+      "license": "(MPL-2.0 OR Apache-2.0)",
+      "optionalDependencies": {
+        "@types/trusted-types": "^2.0.7"
+      }
+    },
     "node_modules/dunder-proto": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/dunder-proto/-/dunder-proto-1.0.1.tgz",