Add dark mode support and replace group assignment with playlist assignment

- Added comprehensive dark mode styling to all pages:
  * Dashboard (workflow guide, secondary text, log items)
  * Admin panel with user management system
  * Content/playlist management page
  * Upload media page
  * Add player page

- Implemented user management system:
  * Create/edit/delete users
  * Two role types (user/admin)
  * Reset password functionality
  * Role-based permissions

- Replaced group assignment with playlist assignment:
  * Players now directly assigned to playlists
  * Updated add player form and backend
  * Removed group selection from player creation

- Fixed bugs:
  * Updated instance_path configuration for SQLite
  * Fixed import path in app factory
  * Updated dependencies (Pillow 11.0.0, removed gevent)

- Added start.sh script for easy development server launch

app/templates/content/content_list_new.html

@@ -50,6 +50,15 @@
         transform: translateX(5px);
     }
     
+    body.dark-mode .playlist-item {
+        background: #1a202c;
+        border-left-color: #7c3aed;
+    }
+    
+    body.dark-mode .playlist-item:hover {
+        background: #2d3748;
+    }
+    
     .playlist-info h3 {
         margin: 0 0 5px 0;
         font-size: 18px;
@@ -60,6 +69,10 @@
         color: #6c757d;
     }
     
+    body.dark-mode .playlist-stats {
+        color: #a0aec0;
+    }
+    
     .playlist-actions {
         display: flex;
         gap: 10px;
@@ -75,12 +88,22 @@
         font-weight: 600;
     }
     
+    body.dark-mode .form-group label {
+        color: #e2e8f0;
+    }
+    
+    body.dark-mode small {
+        color: #a0aec0;
+    }
+    
     .form-control {
         width: 100%;
         padding: 10px;
         border: 1px solid #ced4da;
         border-radius: 4px;
         font-size: 14px;
+        background: white;
+        color: #2d3748;
     }
     
     .form-control:focus {
@@ -89,6 +112,17 @@
         box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
     }
     
+    body.dark-mode .form-control {
+        background: #1a202c;
+        border-color: #4a5568;
+        color: #e2e8f0;
+    }
+    
+    body.dark-mode .form-control:focus {
+        border-color: #7c3aed;
+        box-shadow: 0 0 0 3px rgba(124, 58, 237, 0.2);
+    }
+    
     textarea.form-control {
         resize: vertical;
         min-height: 80px;
@@ -161,6 +195,16 @@
         box-shadow: 0 4px 8px rgba(0,0,0,0.1);
     }
     
+    body.dark-mode .media-item {
+        background: #2d3748;
+        border-color: #4a5568;
+    }
+    
+    body.dark-mode .media-item:hover {
+        border-color: #7c3aed;
+        box-shadow: 0 4px 8px rgba(0,0,0,0.3);
+    }
+    
     .media-icon {
         font-size: 48px;
         margin-bottom: 10px;
@@ -170,6 +214,33 @@
         font-size: 12px;
         word-break: break-word;
     }
+    
+    body.dark-mode .media-name {
+        color: #e2e8f0;
+    }
+    
+    /* Table styling for dark mode */
+    body.dark-mode table thead tr {
+        background: #1a202c !important;
+    }
+    
+    body.dark-mode table th {
+        color: #e2e8f0;
+        border-bottom-color: #4a5568 !important;
+    }
+    
+    body.dark-mode table tbody tr {
+        border-bottom-color: #4a5568 !important;
+    }
+    
+    body.dark-mode table td {
+        color: #e2e8f0;
+    }
+    
+    body.dark-mode code {
+        background: #1a202c !important;
+        color: #e2e8f0;
+    }
 </style>
 
 <div class="container" style="max-width: 1400px;">