feat(typescript): implement type-safe database error handling and eliminate any types

- Add comprehensive database error interfaces (DatabaseConstraintError, DatabaseStorageError, DexieError)
- Implement type guards for database error handling (isDatabaseError, isDatabaseConstraintError, etc.)
- Replace any types with proper TypeScript types in ContactsView, ProjectsView, and IdentitySwitcherView
- Implement type-safe error handling patterns using new type guards
- Fix dynamic property access with keyof operator for type safety

Resolves Priority 1 type safety issues in database operations, project management, and identity switching.

src/views/IdentitySwitcherView.vue

@@ -234,7 +234,9 @@ export default class IdentitySwitcherView extends Vue {
           {
             did,
             settingsKeys: Object.keys(newSettings).filter(
-              (k) => (newSettings as any)[k] !== undefined,
+              (k) =>
+                k in newSettings &&
+                newSettings[k as keyof typeof newSettings] !== undefined,
             ),
           },
         );