Fix: add grid_size to allowed backend settings and remove auto-save

backend/handlers/settings.go

@@ -40,6 +40,7 @@ func (h *SettingsHandler) UpdateSettings(c *fiber.Ctx) error {
 
 	allowedKeys := map[string]bool{
 		"theme":                    true,
+		"grid_size":                true,
 		"trash_auto_purge_days":    true,
 		"pinned_sidebar_expanded":  true,
 		"pinned_order":             true,

frontend/src/components/SettingsPage.tsx

@@ -136,8 +136,6 @@ export default function SettingsPage({ onLogout }: SettingsPageProps) {
               step="10"
               value={settings.grid_size}
               onChange={(e) => setSettings({ ...settings, grid_size: e.target.value })}
-              onMouseUp={handleSave}
-              onTouchEnd={handleSave}
               className="w-full max-w-xs accent-[var(--color-accent)]"
             />
           </div>