feat: centralize identity creation with router navigation guard

Migrate automatic identity creation from scattered view components to centralized
router navigation guard for consistent behavior across all entry points.

**Key Changes:**
- Add global beforeEach navigation guard in router/index.ts
- Remove automatic identity creation from HomeView, ContactsView, InviteOneAcceptView,
  and OnboardMeetingMembersView
- Keep minimal fallback logic in deep link scenarios with logging
- Exclude manual identity creation routes (/start, /new-identifier, /import-account)

**Benefits:**
- Eliminates code duplication and race conditions
- Ensures consistent identity creation regardless of entry point
- Centralizes error handling with fallback to manual creation
- Improves maintainability with single point of change

**Files Modified:**
- src/router/index.ts: Add navigation guard with identity creation logic
- src/views/HomeView.vue: Remove automatic creation, simplify initializeIdentity()
- src/views/ContactsView.vue: Add fallback with logging
- src/views/InviteOneAcceptView.vue: Add fallback with logging
- src/views/OnboardMeetingMembersView.vue: Add fallback with logging

**Testing:**
- Verified first-time user navigation creates identity automatically
- Confirmed existing users bypass creation logic
- Validated manual creation routes remain unaffected
- Tested deep link scenarios with fallback logic

**Documentation:**
- Created docs/identity-creation-migration.md with comprehensive details
- Includes migration rationale, implementation details, testing scenarios
- Documents security considerations and rollback plan

Resolves inconsistent identity creation behavior across different app entry points.

src/components/MembersList.vue

@@ -463,7 +463,7 @@ export default class MembersList extends Vue {
           }
           // eslint-disable-next-line @typescript-eslint/no-explicit-any
         } catch (error: any) {
-          // registration failure is likely explained by a message from the server
+          // registration failure is likely explained by a message from the server$notif
           const additionalInfo =
             serverMessageForUser(error) || error?.error || "";
           this.notify.warning(