feat: Add comprehensive Database Migration UI component

- Create DatabaseMigration.vue with vue-facing-decorator and Tailwind CSS
- Add complete UI for comparing and migrating data between Dexie and SQLite
- Implement real-time loading states, error handling, and success feedback
- Add navigation link to Account page for easy access
- Include export functionality for comparison data
- Create comprehensive documentation in doc/database-migration-guide.md
- Fix all linting issues and ensure code quality standards
- Support both contact and settings migration with overwrite options
- Add visual difference analysis with summary cards and detailed breakdowns

The component provides a professional interface for the migrationService.ts,
enabling users to safely transfer data between database systems during
the transition from Dexie to SQLite storage.

src/views/AccountViewView.vue

@@ -953,6 +953,12 @@
       >
         Logs
       </router-link>
+      <router-link
+        :to="{ name: 'database-migration' }"
+        class="block w-fit text-center text-md bg-gradient-to-b from-slate-400 to-slate-700 shadow-[inset_0_-1px_0_0_rgba(0,0,0,0.5)] text-white px-4 py-2 rounded-md mt-2"
+      >
+        Database Migration
+      </router-link>
       <router-link
         :to="{ name: 'test' }"
         class="block w-fit text-center text-md bg-gradient-to-b from-slate-400 to-slate-700 shadow-[inset_0_-1px_0_0_rgba(0,0,0,0.5)] text-white px-4 py-2 rounded-md mt-2"