[Medium]: Replace hash-based profile navigation with app state navigation

### Problem Statement

Profile action buttons currently use hash-based navigation. The app itself uses page state navigation, so behavior is inconsistent and harder to maintain.

### Proposed Approach

Add a page navigation callback in App and pass it to UserProfile.
Replace hash-based button handlers with callback-based page switching.
Make Create Your First Event open create-event page.
Make Browse Events open event-list page.
Remove any active hash navigation usage related to these buttons.
Verify navigation works in authenticated flow.

### Files and Scope

event-dappp/src/App.js
event-dappp/src/components/UserProfile.jsx

### Acceptance Criteria

- [ ] Create Your First Event button navigates through app state
- [ ] Browse Events button navigates through app state
- [ ] No active hash navigation is used for profile actions
- [ ] Navigation works correctly after login

### Test Plan

Open profile page after login.
Click Create Your First Event and confirm create-event page opens.
Click Browse Events and confirm event-list page opens.
Confirm URL hash is not used for these actions.

### Risks and Edge Cases

Possible regression in page switching if callback is not passed correctly.
Must ensure behavior still works when user is not authenticated.

Start by reading event-dappp/src/App.js and event-dappp/src/components/UserProfile.jsx to trace current page-state and hash navigation. Update the profile actions to use the app navigation callback, then follow the test plan after login: both buttons should open their target pages without changing the URL hash, including for unauthenticated users.

Written by the indexing model from the issue text.