refactor: rename bruno/auth folder to bruno/user

The auth folder now contains user management endpoints beyond just authentication:
- User registration/login (auth)
- Profile management (user)
- Theme settings (user preferences)
- Ebook folder management (user settings)

Renaming to 'user' better reflects the expanded scope covering user accounts, preferences, and settings management.

bruno/user/Delete Ebook Folder.bru

@@ -0,0 +1,40 @@
+meta {
+  name: Delete Ebook Folder
+  type: http
+  seq: 7
+}
+
+delete {
+  url: {{base_url}}/api/auth/ebook-folders/{{folder_path}}
+  body: none
+  auth: inherit
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Delete Ebook Folder
+
+  Removes an ebook folder for the authenticated user.
+
+  **Method:** DELETE
+
+  **Endpoint:** /api/auth/ebook-folders/:folderPath
+
+  **Authentication:** Required
+
+  **URL Parameters:**
+  - `folderPath` (string): URL-encoded folder path to remove
+
+  **Response:**
+  - `message` (string): Success message
+
+  **Status Codes:**
+  - 200: Success
+  - 400: Bad Request
+  - 401: Unauthorized
+  - 404: Folder not found
+}