feat: Implement timeout handling and background processing for update feature

UPDATE_FIX_SUMMARY.md

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+# Update Feature Fixes - Final Summary
+
+## Problem Identified
+The update feature was causing the application to hang indefinitely when clicked. The issue had two components:
+
+1. **UI Thread Blocking**: The original code was running download operations synchronously on the UI thread
+2. **Network Timeout Issues**: Even with timeouts set, the socket-level network calls would hang indefinitely if the server didn't respond
+
+## Solutions Implemented
+
+### 1. Background Threading (First Fix)
+- Created `UpdateDownloadWorker` class to run download operations in a background thread
+- Moved blocking network calls off the UI thread
+- This prevents the UI from freezing while waiting for network operations
+
+### 2. Aggressive Timeout Strategy (Second Fix)
+Applied timeouts at multiple levels to ensure the app never hangs:
+
+#### A. Socket-Level Timeout (Most Important)
+- **File**: `src/webdrop_bridge/core/updater.py`
+- Reduced `urlopen()` timeout from 10 seconds to **5 seconds**
+- This is the first line of defense against hanging socket connections
+- Applied in `_fetch_release()` method
+
+#### B. Asyncio-Level Timeout
+- **File**: `src/webdrop_bridge/ui/main_window.py` and `src/webdrop_bridge/core/updater.py`
+- `UpdateCheckWorker`: 10-second timeout on entire check operation
+- `UpdateDownloadWorker`: 300-second timeout on download, 30-second on verification
+- `check_for_updates()`: 8-second timeout on async executor
+- These catch any remaining hangs in the asyncio operations
+
+#### C. Qt-Level Timeout (Final Safety Net)
+- **File**: `src/webdrop_bridge/ui/main_window.py`
+- Update check: **30-second QTimer** safety timeout (`_run_async_check()`)
+- Download: **10-minute QTimer** safety timeout (`_perform_update_async()`)
+- If nothing else works, Qt's event loop will forcefully close the operation
+
+### 3. Error Handling Improvements
+- Added proper exception handling for `asyncio.TimeoutError`
+- Better logging to identify where hangs occur
+- User-friendly error messages like "no server response" or "Operation timed out"
+- Graceful degradation: operations fail fast instead of hanging
+
+## Timeout Hierarchy (in seconds)
+```
+Update Check Flow:
+  QTimer safety net: 30s ─┐
+                          ├─ Asyncio timeout: 10s ─┐
+                                                   ├─ Socket timeout: 5s (first to trigger)
+Download Flow:
+  QTimer safety net: 600s ─┐
+                           ├─ Asyncio timeout: 300s ─┐
+                                                     ├─ Socket timeout: 5s (first to trigger)
+```
+
+## Files Modified
+1. **src/webdrop_bridge/ui/main_window.py**
+   - Updated `UpdateCheckWorker.run()` with timeout handling
+   - Updated `UpdateDownloadWorker.run()` with timeout handling
+   - Added QTimer safety timeouts in `_run_async_check()` and `_perform_update_async()`
+   - Proper event loop cleanup in finally blocks
+
+2. **src/webdrop_bridge/core/updater.py**
+   - Reduced socket timeout in `_fetch_release()` from 10s to 5s
+   - Added timeout to `check_for_updates()` async operation
+   - Added timeout to `download_update()` async operation
+   - Added timeout to `verify_checksum()` async operation
+   - Better error logging with exception types
+
+## Testing
+- All 7 integration tests pass
+- Timeout verification script confirms all timeout mechanisms are in place
+- No syntax errors in modified code
+
+## Result
+The application will no longer hang indefinitely when checking for or downloading updates. Instead:
+- Operations timeout quickly (5-30 seconds depending on operation type)
+- User gets clear feedback about what went wrong
+- User can retry or cancel without force-killing the app
+- Background threads are properly cleaned up to avoid resource leaks