refactor: Improve voice and response modals UX

- Center both modals with dark backdrop and blur effect
- Make voice modal larger (420px) with bigger record button
- Make response modal larger (540px) with bigger text (18px)
- Remove auto-dismiss from bubbles - manual dismiss only
- Add backdrop click to close response modal
- Remove unused bottom sheet code from FloatingVoice
- Add touch protection CSS to prevent text selection
- Clean up mobile-specific variables no longer needed

frontend/src/services/tools/handlers/responseHandlers.ts

@@ -10,7 +10,6 @@ export interface ResponseControls {
   removeMessage: (id: string) => void
   clearAll: () => void
   getMessages: () => Array<{ id: string; message: string; type: string; timestamp: number }>
-  move: (x: number, y: number) => void
 }
 
 // Global reference to response controls (set by App.vue)