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/sync-kobo/get-unlinked-books.bru

@@ -1,5 +1,5 @@
 meta {
-  name: "Get Unlinked Books - User View"
+  name: Get Unlinked Books - User View
   type: http
   seq: 4
 }
@@ -7,15 +7,54 @@ meta {
 get {
   url: {{base_url}}/api/sync/unlinked-books
   body: none
-  auth: {
-    type: bearer
-    bearer: {{user_token}}
-  }
+  auth: inherit
 }
 
-assert {
-  response.status == 200
-  response.body.unlinked exists()
-  response.body.total exists()
-  response.body.total >= 0
+headers {
+  Authorization: Bearer {{user_token}}
+  Content-Type: application/json
+}
+
+script:post-response {
+  function onResponse(res) {
+    if (res.getStatus() === 200) {
+      const body = res.getBody();
+      tests('Has unlinked array', body.unlinked !== undefined);
+      tests('Has total count', body.total !== undefined);
+      tests('Total >= 0', body.total >= 0);
+    }
+  }
+  onResponse(res);
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Get Unlinked Books - User View
+
+  Retrieves all unlinked books for the authenticated user that need manual linking.
+
+  **Method:** GET
+
+  **Endpoint:** /api/sync/unlinked-books
+
+  **Authentication:** Bearer token
+
+  **Response:**
+  - `unlinked` (array): Array of unlinked book objects
+    - `id` (string): Unlinked book UUID
+    - `title` (string): Book title
+    - `author` (string): Book author
+    - `device_id` (string): Source device ID
+    - `device_name` (string): Source device name
+    - `detected_at` (string): Detection timestamp
+  - `total` (number): Total count of unlinked books
+
+  **Status Codes:**
+  - 200: Success
+  - 401: Unauthorized
+  - 500: Internal server error
 }