feat: Implement sidebar collapse and expand functionality

- Add CSS for collapsed sidebar state and transitions
- Introduce SidebarToggle class for managing collapse/expand logic
- Integrate SidebarToggle initialization in main script
- Add toggle button to navbar and make mini sidebar clickable
- Store sidebar collapsed state in localStorage
- Filter image files and directories in view mode via FileTree
- Make navbar brand clickable to navigate to collection root or home

static/js/config.js

@@ -5,86 +5,86 @@
 
 const Config = {
     // ===== TIMING CONFIGURATION =====
-    
+
     /**
      * Long-press threshold in milliseconds
      * Used for drag-and-drop detection in file tree
      */
     LONG_PRESS_THRESHOLD: 400,
-    
+
     /**
      * Debounce delay in milliseconds
      * Used for editor preview updates
      */
     DEBOUNCE_DELAY: 300,
-    
+
     /**
      * Toast notification duration in milliseconds
      */
     TOAST_DURATION: 3000,
-    
+
     /**
      * Mouse move threshold in pixels
      * Used to detect if user is dragging vs clicking
      */
     MOUSE_MOVE_THRESHOLD: 5,
-    
+
     // ===== UI CONFIGURATION =====
-    
+
     /**
      * Drag preview width in pixels
      * Width of the drag ghost image during drag-and-drop
      */
     DRAG_PREVIEW_WIDTH: 200,
-    
+
     /**
      * Tree indentation in pixels
      * Indentation per level in the file tree
      */
     TREE_INDENT_PX: 12,
-    
+
     /**
      * Toast container z-index
      * Ensures toasts appear above other elements
      */
     TOAST_Z_INDEX: 9999,
-    
+
     /**
      * Minimum sidebar width in pixels
      */
     MIN_SIDEBAR_WIDTH: 150,
-    
+
     /**
      * Maximum sidebar width as percentage of container
      */
     MAX_SIDEBAR_WIDTH_PERCENT: 40,
-    
+
     /**
      * Minimum editor width in pixels
      */
     MIN_EDITOR_WIDTH: 250,
-    
+
     /**
      * Maximum editor width as percentage of container
      */
     MAX_EDITOR_WIDTH_PERCENT: 70,
-    
+
     // ===== VALIDATION CONFIGURATION =====
-    
+
     /**
      * Valid filename pattern
      * Only lowercase letters, numbers, underscores, and dots allowed
      */
     FILENAME_PATTERN: /^[a-z0-9_]+(\.[a-z0-9_]+)*$/,
-    
+
     /**
      * Characters to replace in filenames
      * All invalid characters will be replaced with underscore
      */
     FILENAME_INVALID_CHARS: /[^a-z0-9_.]/g,
-    
+
     // ===== STORAGE KEYS =====
-    
+
     /**
      * LocalStorage keys used throughout the application
      */
@@ -93,99 +93,104 @@ const Config = {
          * Dark mode preference
          */
         DARK_MODE: 'darkMode',
-        
+
         /**
          * Currently selected collection
          */
         SELECTED_COLLECTION: 'selectedCollection',
-        
+
         /**
          * Last viewed page (per collection)
          * Actual key will be: lastViewedPage:{collection}
          */
         LAST_VIEWED_PAGE: 'lastViewedPage',
-        
+
         /**
          * Column dimensions (sidebar, editor, preview widths)
          */
-        COLUMN_DIMENSIONS: 'columnDimensions'
+        COLUMN_DIMENSIONS: 'columnDimensions',
+
+        /**
+         * Sidebar collapsed state
+         */
+        SIDEBAR_COLLAPSED: 'sidebarCollapsed'
     },
-    
+
     // ===== EDITOR CONFIGURATION =====
-    
+
     /**
      * CodeMirror theme for light mode
      */
     EDITOR_THEME_LIGHT: 'default',
-    
+
     /**
      * CodeMirror theme for dark mode
      */
     EDITOR_THEME_DARK: 'monokai',
-    
+
     /**
      * Mermaid theme for light mode
      */
     MERMAID_THEME_LIGHT: 'default',
-    
+
     /**
      * Mermaid theme for dark mode
      */
     MERMAID_THEME_DARK: 'dark',
-    
+
     // ===== FILE TREE CONFIGURATION =====
-    
+
     /**
      * Default content for new files
      */
     DEFAULT_FILE_CONTENT: '# New File\n\n',
-    
+
     /**
      * Default filename for new files
      */
     DEFAULT_NEW_FILENAME: 'new_file.md',
-    
+
     /**
      * Default folder name for new folders
      */
     DEFAULT_NEW_FOLDERNAME: 'new_folder',
-    
+
     // ===== WEBDAV CONFIGURATION =====
-    
+
     /**
      * WebDAV base URL
      */
     WEBDAV_BASE_URL: '/fs/',
-    
+
     /**
      * PROPFIND depth for file tree loading
      */
     PROPFIND_DEPTH: 'infinity',
-    
+
     // ===== DRAG AND DROP CONFIGURATION =====
-    
+
     /**
      * Drag preview opacity
      */
     DRAG_PREVIEW_OPACITY: 0.8,
-    
+
     /**
      * Dragging item opacity
      */
     DRAGGING_OPACITY: 0.4,
-    
+
     /**
      * Drag preview offset X in pixels
      */
     DRAG_PREVIEW_OFFSET_X: 10,
-    
+
     /**
      * Drag preview offset Y in pixels
      */
     DRAG_PREVIEW_OFFSET_Y: 10,
-    
+
     // ===== NOTIFICATION TYPES =====
-    
+
     /**
      * Bootstrap notification type mappings
      */