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/media-items/Delete Media Rating.bru

@@ -0,0 +1,67 @@
+meta {
+  name: Delete Media Rating
+  type: http
+  seq: 5
+}
+
+delete {
+  url: {{base_url}}/api/media-items/{{media_item_id}}/rating
+  body: none
+  auth: inherit
+}
+
+headers {
+  Content-Type: application/json
+}
+
+tests {
+  test_delete_media_rating_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 {
+  mediaItemId: "550e8400-e29b-41d4-a716-446655440000"
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Delete Media Rating
+  
+  Deletes a user's rating for a specific media item.
+  
+  **Method:** DELETE
+  
+  **Endpoint:** /api/media-items/{id}/rating
+  
+  **Authentication:** Required (Bearer token)
+  
+  **Path Parameters:**
+  - `id` (string): Media item UUID
+  
+  **Response:** Empty (204 No Content)
+  
+  **Status Codes:**
+  - 204: Rating deleted successfully
+  - 401: Unauthorized
+  - 404: Media item not found
+  - 500: Internal server error
+  
+  **Examples:**
+  - Delete media rating: `DELETE /api/media-items/550e8400-e29b-41d4-a716-446655440000/rating`
+  
+  **Note:** Deletes only the authenticated user's rating, not other users' ratings.
+}