feat: implement Preview module dialog and improve submit toast feedback

- Added Preview module dialog showing all configured modules with their content
- Preview shows passages, listening sections, writing tasks, speaking parts
- Displays module badges (timer, difficulty, access type)
- Improved submit toast: shows exam ID, status, and duration (8s)
- Preview button now enabled when a module is active
- Added .vite to .gitignore, added .dockerignore

Made-with: Cursor

.gitignore

@@ -31,3 +31,6 @@ Thumbs.db
 npm-debug.log*
 yarn-debug.log*
 yarn-error.log*
+
+# Vite cache
+.vite/