feat: add comprehensive Bruno API tests for annotations

- Add complete Bruno collection for notes API (5 endpoints)
- Add complete Bruno collection for highlights API (5 endpoints)
- Include detailed request/response documentation
- Add proper validation examples and error cases
- Support both media-items and ebook endpoint testing
- Add environment variable support for dynamic IDs

bruno/highlights/Get Media Highlights.bru

@@ -0,0 +1,51 @@
+meta {
+  name: Get Media Highlights
+  type: http
+  seq: 1
+}
+
+get {
+  url: {{base_url}}/api/media-items/{{media_item_id}}/highlights
+  body: none
+  auth: inherit
+}
+
+script:post-response {
+  onResponse(res);
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Get Media Highlights
+  
+  Retrieves all highlights for a specific media item for the authenticated user.
+  
+  **Method:** GET
+  
+  **Endpoint:** /api/media-items/:id/highlights
+  
+  **Path Parameters:**
+  - `id` (string): Media item ID
+  
+  **Response:**
+  - Array of highlight objects with fields:
+    - `id` (string): Highlight ID
+    - `media_item_id` (string): Media item ID
+    - `user_id` (string): User ID
+    - `selection_text` (string): Highlighted text
+    - `start_position` (string): Start position
+    - `end_position` (string): End position
+    - `color` (string): Highlight color (hex)
+    - `note_id` (string): Optional associated note ID
+    - `created_at` (string): Creation timestamp
+    - `updated_at` (string): Last update timestamp
+  
+  **Status Codes:**
+  - 200: Success
+  - 401: Unauthorized
+  - 404: Media item not found
+}