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/Create Media Highlight.bru

@@ -0,0 +1,59 @@
+meta {
+  name: Create Media Highlight
+  type: http
+  seq: 2
+}
+
+post {
+  url: {{base_url}}/api/media-items/{{media_item_id}}/highlights
+  body: json
+  auth: inherit
+}
+
+body:json {
+  {
+    "selection_text": "This is the highlighted text from the media item.",
+    "start_position": "page:45:offset:120",
+    "end_position": "page:45:offset:145",
+    "color": "#ffff00",
+    "note_id": ""
+  }
+}
+
+script:post-response {
+  onResponse(res);
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## Create Media Highlight
+  
+  Creates a new highlight for a specific media item.
+  
+  **Method:** POST
+  
+  **Endpoint:** /api/media-items/:id/highlights
+  
+  **Path Parameters:**
+  - `id` (string): Media item ID
+  
+  **Request Body:**
+  - `selection_text` (string): Highlighted text (required, 1-5000 chars)
+  - `start_position` (string): Start position (required, max 100 chars)
+  - `end_position` (string): End position (required, max 100 chars)
+  - `color` (string): Highlight color in hex format (optional, default #ffff00)
+  - `note_id` (string): Optional associated note ID
+  
+  **Response:**
+  - Highlight object with all fields including generated ID and timestamps
+  
+  **Status Codes:**
+  - 201: Created
+  - 400: Invalid request
+  - 401: Unauthorized
+  - 404: Media item not found
+}