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/router/index.ts

@@ -143,6 +143,11 @@ const routes: Array<RouteRecordRaw> = [
     name: "logs",
     component: () => import("../views/LogView.vue"),
   },
+  {
+    path: "/database-migration",
+    name: "database-migration",
+    component: () => import("../views/DatabaseMigration.vue"),
+  },
   {
     path: "/new-activity",
     name: "new-activity",