refactor(bruno): migrate API tests to Bruno DSL format

- Convert all existing .bru files from JSON to Bruno DSL format
- Remove obsolete files (conflicts/api.bru, kobo/Kobo Initialization.bru)
- Update auth configuration to use 'inherit' instead of explicit bearer tokens
- Add comprehensive documentation to all test files
- Improve test scripts with proper assertions and error handling

bruno/media-items/EPUB Download.bru

@@ -1,15 +1,42 @@
 meta {
-  name: EPUB Download
+  name: Download EPUB Book
   type: http
   seq: 1
 }
 
-GET {{baseURL}}/api/books/{{bookUUID}}/download
-
-{
-  "meta": {
-    "name": "Download EPUB Book",
-    "description": "Download an EPUB book file from Bookhoard server (no auth required - for Kobo device download)",
-    "documentation": "Kobo devices can download books directly from Bookhoard using this endpoint. The endpoint returns the book file with appropriate Content-Type headers."
-  }
+get {
+  url: {{baseURL}}/api/books/{{bookUUID}}/download
+  body: none
+  auth: none
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Download EPUB Book
+
+  Download an EPUB book file from Bookhoard server. No authentication required for Kobo device downloads.
+
+  **Method:** GET
+
+  **Endpoint:** /api/books/{bookUUID}/download
+
+  **Authentication:** None (for Kobo device downloads)
+
+  **Path Parameters:**
+  - `bookUUID` (string): Book UUID
+
+  **Response:** Binary EPUB file data
+
+  **Response Headers:**
+  - `Content-Type`: application/epub+zip
+
+  **Status Codes:**
+  - 200: Success - EPUB file returned
+  - 404: Book not found
+
+  **Note:** This endpoint is designed for Kobo devices to download books directly from Bookhoard. The endpoint returns the book file with appropriate Content-Type headers.
 }