feat: add Bruno API testing files for multiple folder functionality

- Add auth/Add Ebook Folder.bru - test adding folders to user account
- Add auth/Get Ebook Folders.bru - test listing user's folders
- Add auth/Delete Ebook Folder.bru - test removing folders
- Add scanner/Scan Ebooks.bru - test manual scanning of multiple folders
- Add scanner/Start Scanner.bru - test starting folder monitoring
- Add scanner/Stop Scanner.bru - test stopping folder monitoring
- Update all scanner endpoints to use folder_paths array format

bruno/scanner/Scan Ebooks.bru

@@ -0,0 +1,48 @@
+meta {
+  name: Scan Ebooks
+  type: http
+  seq: 1
+}
+
+post {
+  url: {{base_url}}/api/scanner/scan
+  body: json
+  auth: inherit
+}
+
+body {
+  {
+    "folder_paths": [
+      "/path/to/ebooks",
+      "/another/path/to/ebooks"
+    ]
+  }
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Scan Ebooks
+
+  Manually scans the specified folders for ebooks and adds them to the database.
+
+  **Method:** POST
+
+  **Endpoint:** /api/scanner/scan
+
+  **Authentication:** Required
+
+  **Request Body:**
+  - `folder_paths` (array of strings, required): Array of folder paths to scan
+
+  **Response:**
+  - `message` (string): Success message
+
+  **Status Codes:**
+  - 200: Success
+  - 400: Bad Request
+  - 401: Unauthorized
+}

bruno/scanner/Start Scanner.bru

@@ -0,0 +1,48 @@
+meta {
+  name: Start Scanner
+  type: http
+  seq: 2
+}
+
+post {
+  url: {{base_url}}/api/scanner/start
+  body: json
+  auth: inherit
+}
+
+body {
+  {
+    "folder_paths": [
+      "/path/to/ebooks",
+      "/another/path/to/ebooks"
+    ]
+  }
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Start Scanner
+
+  Starts monitoring the specified folders for ebook changes.
+
+  **Method:** POST
+
+  **Endpoint:** /api/scanner/start
+
+  **Authentication:** Required
+
+  **Request Body:**
+  - `folder_paths` (array of strings, required): Array of folder paths to monitor
+
+  **Response:**
+  - `message` (string): Success message
+
+  **Status Codes:**
+  - 200: Success
+  - 400: Bad Request
+  - 401: Unauthorized
+}

bruno/scanner/Stop Scanner.bru

@@ -0,0 +1,37 @@
+meta {
+  name: Stop Scanner
+  type: http
+  seq: 3
+}
+
+post {
+  url: {{base_url}}/api/scanner/stop
+  body: none
+  auth: inherit
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Stop Scanner
+
+  Stops monitoring folders for ebook changes.
+
+  **Method:** POST
+
+  **Endpoint:** /api/scanner/stop
+
+  **Authentication:** Required
+
+  **Request Body:** None
+
+  **Response:**
+  - `message` (string): Success message
+
+  **Status Codes:**
+  - 200: Success
+  - 401: Unauthorized
+}