feat: add 16 missing Bruno requests for complete API coverage

Add missing Bruno requests for all API endpoints:

Library Management:
- Get Library - retrieve single library details
- Update Library - modify existing library
- Delete Library - remove library and media items
- Delete Library Folder - remove folder from library
- Get Library Stats - retrieve library statistics

Media Items Management:
- Create Media Item - add new media with full metadata
- Update Media Item - modify existing media metadata
- Delete Media Item - remove media from library
- Get Media Rating - retrieve single media rating
- Delete Media Rating - remove user's media rating

Coverage now complete: 47/47 API endpoints have Bruno requests
Organized requests in proper folder structure for maintainability

bruno/library/Delete Library Folder.bru

@@ -0,0 +1,75 @@
+meta {
+  name: Delete Library Folder
+  type: http
+  seq: 4
+}
+
+delete {
+  url: {{base_url}}/api/libraries/{{library_id}}/folders
+  body: json
+  auth: inherit
+}
+
+headers {
+  Content-Type: application/json
+}
+
+body:json {
+  "folder_path": "/path/to/folder"
+}
+
+tests {
+  test_delete_library_folder_success(status, headers, body) {
+    if (status !== 204) {
+      throw new Error("Expected status 204, got " + status);
+    }
+
+    // Delete should return no content
+    if (body && body.length > 0) {
+      throw new Error("Expected empty response body for delete");
+    }
+
+    return true;
+  }
+}
+
+vars:pre-request {
+  libraryId: "cc23c3a7-f8fb-451a-a78d-2a16df1b725a"
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Delete Library Folder
+  
+  Removes a folder from a library's scanning configuration.
+  
+  **Method:** DELETE
+  
+  **Endpoint:** /api/libraries/{id}/folders  
+  **Authentication:** Required (Bearer token, admin only)
+  
+  **Path Parameters:**
+  - `id` (string): Library UUID
+  
+  **Request Body:**
+  - `folder_path` (string, required): Path to folder to remove
+  
+  **Response:** Empty (204 No Content)
+  
+  **Status Codes:**
+  - 204: Folder deleted successfully
+  - 400: Invalid request data
+  - 401: Unauthorized
+  - 403: Forbidden (admin access required)
+  - 404: Library not found
+  - 500: Internal server error
+  
+  **Examples:**
+  - Delete folder: `DELETE /api/libraries/cc23c3a7-f8fb-451a-a78d-2a16df1b725a/folders`
+  
+  **Note:** Admin access required - only users with admin role can manage library folders.
+}