Update v1.2.0-beta - Dynamic context menu & permissions

✨ New Features:
- Dynamic permission-based context menus for files and folders
- Support for collaborative folder access control
- Upload to specific folders including shared folders
- Changelog modal for version updates
- Improved dark mode synchronization

🐛 Bug Fixes:
- Fixed context menu displaying incorrect options
- Fixed CSS !important override preventing dynamic menu behavior
- Fixed folder collaboration permission checks
- Fixed breadcrumb navigation with empty segments
- Fixed "Premature close" error loop in attachments
- Fixed missing user variable in admin routes
- Fixed avatar loading COEP policy issues

🔒 Security:
- Added security middleware (CSRF, rate limiting, input validation)
- Fixed collaboration folder access validation
- Improved shared folder permission handling

🎨 UI/UX Improvements:
- Removed Actions column from folder view
- Context menu now properly hides/shows based on permissions
- Better visual feedback for collaborative folders
- Improved upload flow with inline modals

🧹 Code Quality:
- Added collaboration data to folder routes
- Refactored context menu logic for better maintainability
- Added debug logging for troubleshooting
- Improved file upload handling with chunking support

public/css/dropdown-fixes.css

@@ -0,0 +1,12 @@
+/* Dropdown fixes for dashboard and folder views */
+
+/* Fix pour les dropdowns qui ne s'affichent pas correctement */
+.dropdown-menu {
+    z-index: 1050;
+}
+
+/* Fix pour les menus contextuels */
+.context-menu {
+    position: fixed;
+    z-index: 9999;
+}