feat: add reset button positions to settings

PROBLEM:
- Existing users with saved off-screen FAB positions can't see buttons
- No way to reset positions without clearing all extension settings
- Salixfire and other users on Xiaomi/other devices need safe positions

SOLUTION:
Added "Reset Button Positions" button in Advanced settings section

IMPLEMENTATION:

1. template.html (lines 241-249):
   - Added reset button in Advanced section after Clear Cache button
   - Blue-styled button with rotate icon
   - Help text explains it resets FAB positions to top-left

2. index.js (lines 361-390):
   - Added click handler for reset button
   - Resets all 3 FAB positions to safe top-left defaults:
     * Mobile toggle: top + 20px, left: 12px
     * Refresh: top + 80px, left: 12px
     * Debug: top + 140px, left: 12px
   - Saves settings immediately
   - Applies CSS positions to visible buttons (no page refresh needed)
   - Shows success toast notification

3. style.css (lines 2057-2083, 4123-4125):
   - Added .rpg-btn-reset-fab styles matching clear cache pattern
   - Blue color scheme (vs red for destructive clear cache)
   - Same sizing, padding, transitions as other buttons
   - Mobile responsive font-size with clamp()

USAGE:
Users experiencing off-screen buttons can now:
1. Open RPG Companion settings (gear icon)
2. Scroll to Advanced section
3. Click "Reset Button Positions"
4. All FAB buttons instantly move to safe top-left positions

This fixes the issue for Salixfire and any other users who:
- Have buttons saved in off-screen positions
- Can't scroll to find buttons
- Need to reset without clearing all settings

Works immediately without page refresh or extension reload.

template.html

@@ -237,6 +237,16 @@
                         <i class="fa-solid fa-trash" aria-hidden="true"></i> Clear Extension Cache
                     </button>
                 </div>
+
+                <!-- Reset FAB Positions Button -->
+                <div style="margin-top: 16px; padding-top: 16px; border-top: 1px solid var(--rpg-border);">
+                    <button id="rpg-reset-fab-positions" class="rpg-btn-reset-fab">
+                        <i class="fa-solid fa-arrows-rotate" aria-hidden="true"></i> Reset Button Positions
+                    </button>
+                    <small style="display: block; margin-top: 8px; color: #888; font-size: 11px;">
+                        Resets all floating action buttons (toggle, refresh, debug) to default top-left positions. Useful if buttons are off-screen.
+                    </small>
+                </div>
             </div>
         </div>
     </div>