Builds a release APK and attaches it to GitHub releases automatically.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Remove all iPad-specific UI code and restore simple iPhone-only layout.
The iPad implementation was poorly executed and the settings modal
should be redesigned as a collapsible side toolbar in the future.

Co-Authored-By: Claude Sonnet 4.5 (1M context) <noreply@anthropic.com>

- Fix memory leaks by replacing [self] with [weak self] in all closures
- Add thread safety with operationQueue for dictionary access
- Implement 5-second timeout mechanism for BLE operations to prevent hanging
- Optimize CircularBuffer with caching to reduce array allocations
- Add data validation for BLE bulk data (size and temperature range checks)
- Consolidate settings loading to reduce redundant BLE reads
- Simplify temperature control logic by removing duplicate onChange handler
- Enable native refresh rate for smooth graph scrolling animation
- Clean up all pending operations and timeouts on disconnect

Co-Authored-By: Claude Sonnet 4.5 (1M context) <noreply@anthropic.com>