refactor(dropzone): extract DropzoneInner and unify state management with zustand (#165)

Simplified Dropzone implementation by extracting inner logic to a new component, `DropzoneInner`. Replaced local dropzone state logic with centralized state management using zustand. Adjusted API exports and props accordingly for consistency and maintainability.

app/src/ui/hooks/use-render-count.ts

@@ -0,0 +1,7 @@
+import { useRef } from "react";
+
+export function useRenderCount() {
+   const count = useRef(0);
+   count.current++;
+   return count.current;
+}