Move vote animation to Customize tab as persistent user setting

Replace random animation selection with a user-configurable picker on
the Customize tab between Mood Style and Notifications. Confetti is
the default. Selecting a style shows an inline preview that auto-plays
the animation then dismisses itself. Remove Animation Lab from Settings.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Shared/Models/UserDefaultsStore.swift

@@ -205,6 +205,7 @@ class UserDefaultsStore {
         case healthKitSyncEnabled
         case paywallStyle
         case lockScreenStyle
+        case celebrationAnimation
 
         case contentViewCurrentSelectedHeaderViewBackDays
         case contentViewHeaderTag