Fix bug report bubble overlapping toast notifications

Move the toast container from bottom-4 to bottom-20 so toast
  notifications and upload progress stack above the bug report bubble
  instead of rendering on top of each other.

frontend/src/contexts/ToastContext.tsx

@@ -396,8 +396,8 @@ export function ToastProvider({ children }: { children: ReactNode }) {
     <ToastContext.Provider value={{ showToast, showPersistentToast, dismissToast }}>
       {children}
 
-      {/* Toast Container */}
-      <div className="fixed bottom-4 right-4 z-50 flex flex-col gap-2">
+      {/* Toast Container — positioned above the bug-report bubble */}
+      <div className="fixed bottom-20 right-4 z-50 flex flex-col gap-2">
         {toasts.map((toast) => (
           <div
             key={toast.id}