feat: implement draggable mobile FAB with comprehensive event handling

Add full mouse and touch support for mobile toggle button with drag-to-reposition
functionality and persistent position saving.

Changes:
- Add mobile FAB button with draggable positioning (both mouse and touch)
- Implement time-based drag detection (200ms or 10px threshold)
- Add position persistence in extension settings
- Fix click handler to work on both mobile and desktop viewports
- Add comprehensive diagnostic logging for event debugging
- Update mobile panel to slide from right (matching desktop UX)
- Implement dual-button pattern (FAB + internal collapse toggle)
- Add viewport-constrained dragging with 10px padding
- Prevent click events from firing after drag completion

Mobile UX:
- FAB visible when panel closed, hidden when open
- Internal collapse toggle visible only when panel open
- Touch and mouse drag support with real-time positioning
- Click/tap toggles panel, drag repositions button
- Position saved across sessions

Technical:
- Add mousedown/mousemove/mouseup handlers for desktop drag
- Add touchstart/touchmove/touchend handlers for mobile drag
- Remove broken viewport check that prevented mobile clicks
- Add 'just-dragged' flag to prevent click after drag
- Update .gitignore to exclude CLAUDE.md and .env files

.gitignore

@@ -18,3 +18,9 @@
 
 # Node modules (if any)
 node_modules/
+
+# Environment variables
+.env
+
+# Claude 
+CLAUDE.md