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/sidecar/Download Device Sidecar File.bru

@@ -1,19 +1,61 @@
 meta {
-  name: "Download Device Sidecar File"
+  name: Download Device Sidecar File
   type: http
   seq: 2
 }
 
 get {
   url: {{base_url}}/api/devices/{{device_id}}/sidecar/download
-  auth: {
-    type: bearer
-    bearer: {{user_token}}
-  }
+  body: none
+  auth: inherit
 }
 
-assert {
-  response.status == 200
-  response.headers["Content-Type"] contains "application/json"
-  response.headers["Content-Disposition"] contains ".bookhoard.json"
+headers {
+  Authorization: Bearer {{user_token}}
+  Content-Type: application/json
+}
+
+script:post-response {
+  function onResponse(res) {
+    if (res.getStatus() === 200) {
+      const headers = res.getHeaders();
+      const contentType = headers.get("Content-Type");
+      const contentDisposition = headers.get("Content-Disposition");
+      tests('Content-Type is JSON', contentType && contentType.includes("application/json"));
+      tests('Has .bookhoard.json filename', contentDisposition && contentDisposition.includes(".bookhoard.json"));
+    }
+  }
+  onResponse(res);
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Download Device Sidecar File
+
+  Downloads the sidecar configuration file for a device in JSON format.
+
+  **Method:** GET
+
+  **Endpoint:** /api/devices/{device_id}/sidecar/download
+
+  **Authentication:** Bearer token
+
+  **Path Parameters:**
+  - `device_id` (string): Device UUID
+
+  **Response Headers:**
+  - `Content-Type`: application/json
+  - `Content-Disposition`: attachment; filename="device.bookhoard.json"
+
+  **Response Body:** JSON sidecar configuration file
+
+  **Status Codes:**
+  - 200: Success - file returned
+  - 401: Unauthorized
+  - 404: Device not found
+  - 500: Internal server error
 }