feat: expand internationalization and add identity management

This release significantly expands internationalization support and adds comprehensive identity management features.

Internationalization (i18n):
- Add 5 new languages: Spanish, Italian, German, Dutch, Portuguese
- Expand from 3 to 8 total supported languages
- Redesign language switcher for better scalability (dropdown UI)
- Complete translations for all features across all languages

Identity Management:
- Multiple sender identities with per-identity signatures
- Sub-addressing support (user+tag@domain.com)
- Context-aware tag suggestions for sub-addresses
- Identity badges in email viewer and list
- Full CRUD operations for managing identities

Newsletter Management:
- RFC 2369 List-Unsubscribe support (one-click unsubscribe)
- HTTP and mailto unsubscribe methods
- Security validation prevents XSS attacks
- Two-step confirmation with persistent dismissal

Security & Accessibility:
- Dark mode email readability (intelligent color transformation)
- WCAG 2.0 Level AA color contrast compliance
- Comprehensive XSS prevention with validation utilities
- Unit test coverage for security-critical code (57 validation tests)

Testing:
- Add unit tests for validation utilities
- Add unit tests for email sanitization
- Add unit tests for color transformation
- Full test coverage for XSS attack vectors

package.json

@@ -34,31 +34,38 @@
     "@types/dompurify": "^3.0.5",
     "clsx": "^2.1.1",
     "date-fns": "^4.1.0",
-    "dompurify": "^3.2.7",
+    "dompurify": "^3.3.1",
     "jmap-jam": "^0.13.1",
     "lucide-react": "^0.562.0",
     "next": "^16.0.8",
-    "next-auth": "^4.24.11",
     "next-intl": "^4.5.8",
     "react": "^19.2.1",
     "react-dom": "^19.2.1",
-    "tailwind-merge": "^3.3.1",
+    "sonner": "^2.0.7",
+    "tailwind-merge": "^3.4.0",
     "zustand": "^5.0.9"
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
+    "@testing-library/dom": "^10.4.1",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.1",
     "@types/node": "^22",
-    "@types/react": "^19",
-    "@types/react-dom": "^19",
+    "@types/react": "^19.2.7",
+    "@types/react-dom": "^19.2.3",
     "@typescript-eslint/eslint-plugin": "^8.49.0",
     "@typescript-eslint/parser": "^8.49.0",
+    "@vitejs/plugin-react": "^5.1.2",
+    "@vitest/ui": "^4.0.16",
     "eslint": "^9.39.1",
     "eslint-config-next": "^16.0.8",
     "eslint-plugin-react": "^7.37.5",
-    "globals": "^16.5.0",
+    "globals": "^17.0.0",
     "husky": "^9.1.7",
+    "jsdom": "^27.4.0",
     "lint-staged": "^16.2.7",
     "tailwindcss": "^4.1.17",
-    "typescript": "^5"
+    "typescript": "^5.9.3",
+    "vitest": "^4.0.16"
   }
 }