Fix notification and sound system issues with comprehensive improvements

- **Fixed duplicate sound events**: Prevent success/shutdown sounds from playing multiple times during timeline switches and app quit
- **Added event coordination patterns**: Implemented flags and source tracking to prevent circular UI event chains
- **Completed sound event coverage**: Added missing sound methods (play_favorite, play_follow, play_unfollow, play_direct_message, play_post) and wired them to user actions
- **Enhanced notification system**: Fixed desktop notifications ignoring enable/disable settings by adding missing notifications section to default config
- **Improved timeline-specific sounds**: Conversations now use direct_message sound instead of generic timeline_update sound
- **Added duplicate code prevention guidelines**: Comprehensive CLAUDE.md section with patterns, checklist, and testing requirements to prevent future duplicate implementations
- **Sound pack compatibility**: Full support for both default pack (private_message, post_sent) and Doom pack (direct_message, post) naming conventions with intelligent fallback

All sound events now properly trigger on user actions: boost/favorite posts, follow/unfollow users, notifications, timeline updates, and lifecycle events.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

CLAUDE.md

@@ -7,6 +7,74 @@ Bifrost is a fully accessible fediverse client built with PySide6, designed spec
 - Check for any changes in git project before doing anything else. Make sure the latest changes have been pulled
 - See what has changed, use git commands and examine the code to make sure you are up to date with the latest code
 
+## Duplicate Code Prevention Guidelines
+
+### Critical Areas Requiring Attention
+1. **Sound/Audio Events**: Never add multiple paths that trigger the same sound event
+2. **UI Event Handlers**: Avoid circular event chains (A triggers B which triggers A)
+3. **Timeline Operations**: Coordinate refresh calls and state changes to prevent conflicts
+4. **Lifecycle Events**: Ensure shutdown, close, and quit events don't overlap
+
+### Required Patterns for Event-Heavy Operations
+
+#### Event Coordination Pattern
+```python
+def operation_method(self):
+    if hasattr(self, '_operation_in_progress') and self._operation_in_progress:
+        return
+    self._operation_in_progress = True
+    try:
+        # perform operation
+        self.sound_manager.play_success()
+    finally:
+        # Reset flag after brief delay to prevent rapid-fire calls
+        QTimer.singleShot(100, lambda: setattr(self, '_operation_in_progress', False))
+```
+
+#### Event Source Tracking Pattern
+```python
+def ui_triggered_method(self, index, from_source="unknown"):
+    # Handle differently based on source: "tab_change", "keyboard", "menu"
+    if from_source == "tab_change":
+        # Skip certain UI updates to prevent circular calls
+        pass
+```
+
+#### Lifecycle Event Coordination Pattern
+```python
+def quit_application(self):
+    self._shutdown_handled = True  # Mark that shutdown is being handled
+    self.sound_manager.play_shutdown()
+    
+def closeEvent(self, event):
+    # Only handle if not already handled by explicit quit
+    if not hasattr(self, '_shutdown_handled'):
+        self.sound_manager.play_shutdown()
+```
+
+### Development Review Checklist
+Before implementing any sound, notification, or UI event:
+1. **Is there already another code path that triggers this same feedback?**
+2. **Could this create an event loop (A calls B which calls A)?**
+3. **Can rapid user actions (keyboard shortcuts) trigger this multiple times?**
+4. **Does this operation need coordination with other similar operations?**
+5. **Are there multiple UI elements (menu + button + shortcut) that trigger this?**
+
+### Common Patterns to Avoid
+- Multiple event handlers calling the same sound method
+- UI updates that trigger their own event handlers
+- Shutdown/close/quit events without coordination
+- Timeline refresh without checking if already refreshing
+- Direct sound calls in multiple places for the same user action
+
+### Testing Requirements
+When adding event-driven features, always test:
+- Rapid keyboard shortcut usage
+- Multiple quick UI interactions  
+- Combinations of keyboard shortcuts + UI clicks
+- Window closing during operations
+- Tab switching with keyboard vs mouse
+
 ## Documentation and Dependencies
 - **README Updates**: When adding new functionality or sound events, update README.md with detailed descriptions
 - **Requirements Management**: Check and update requirements.txt when new dependencies are added