refactor: Modularize UI components and utilities

- Extract UI components into separate JS files
- Centralize configuration values in config.js
- Introduce a dedicated logger module
- Improve file tree drag-and-drop and undo functionality
- Refactor modal handling to a single manager
- Add URL routing support for SPA navigation
- Implement view mode for read-only access

server_webdav.py

@@ -78,27 +78,36 @@ class MarkdownEditorApp:
         # Root and index.html
         if path == '/' or path == '/index.html':
             return self.handle_index(environ, start_response)
-        
+
         # Static files
         if path.startswith('/static/'):
             return self.handle_static(environ, start_response)
-        
+
         # Health check
         if path == '/health' and method == 'GET':
             start_response('200 OK', [('Content-Type', 'text/plain')])
             return [b'OK']
-            
+
         # API for collections
         if path == '/fs/' and method == 'GET':
             return self.handle_collections_list(environ, start_response)
 
+        # Check if path starts with a collection name (for SPA routing)
+        # This handles URLs like /notes/ttt or /documents/file.md
+        # MUST be checked BEFORE WebDAV routing to prevent WebDAV from intercepting SPA routes
+        path_parts = path.strip('/').split('/')
+        if path_parts and path_parts[0] in self.collections:
+            # This is a SPA route for a collection, serve index.html
+            # The client-side router will handle the path
+            return self.handle_index(environ, start_response)
+
         # All other /fs/ requests go to WebDAV
         if path.startswith('/fs/'):
             return self.webdav_app(environ, start_response)
 
-        # Fallback for anything else (shouldn't happen with correct linking)
-        start_response('404 Not Found', [('Content-Type', 'text/plain')])
-        return [b'Not Found']
+        # Fallback: Serve index.html for all other routes (SPA routing)
+        # This allows client-side routing to handle any other paths
+        return self.handle_index(environ, start_response)
     
     def handle_collections_list(self, environ, start_response):
         """Return list of available collections"""