Refactor App layout and enhance UI components for better usability

- Changed the default active tab in the App component from 'profiles' to 'main'.
- Improved the layout of the main content area to better accommodate different views, including profiles, generation forms, and history.
- Updated Sidebar component to reflect the new tab structure with a 'main' tab.
- Enhanced the GenerationForm to utilize the selected profile from the UI store, improving user feedback when no profile is selected.
- Added a new CircleButton component for better icon button interactions.
- Adjusted styles in various components for improved responsiveness and visual consistency.

app/src/index.css

@@ -102,6 +102,10 @@
   * {
     @apply border-border;
   }
+  html,
+  body {
+    @apply overflow-hidden;
+  }
   body {
     @apply bg-background text-foreground;
   }