Add cancel button on project loading screen after 3 second delay

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## Summary

When loading a project takes longer than expected, users have no way to cancel the operation or return to the home screen. Add a button that appears after 3 seconds of loading time, allowing users to abort and return to the projects list.

## Current Behavior

The project loading screen shows a logo and "Opening project ..." text. Users must wait for loading to complete or fail with no option to cancel.

## Proposed Enhancement

Add a cancel button that appears after 3 seconds of loading.

### Button Naming

**Recommendation: "Cancel"** - universally understood and matches the action of aborting an in-progress operation.

Alternatives considered: "Go Back", "Back to Projects", "Close"

### Button Position

To be defined by design.

## Acceptance Criteria

- Cancel button is not visible when loading screen first appears
- Cancel button becomes visible after 3 seconds of loading
- Tapping the cancel button aborts the loading operation
- User is returned to the projects list after cancellation

Start by locating the project loading screen entry point and the existing project-loading operation; the issue names no file or test. Run the app and verify that the cancel control appears only after three seconds, aborts loading, and returns the user to the projects list.

Written by the indexing model from the issue text.