docs(api): add KOReader sync protocol documentation

- sync_progress.md - POST /api/sync/koreader/progress
- get_metadata.md - GET /api/sync/koreader/metadata/:uuid
- get_library.md - GET /api/sync/koreader/library
- sync_bookmarks.md - POST /api/sync/koreader/bookmarks

KOReader device sync endpoints with device authentication
for progress, metadata, library, and bookmarks

docs/developer/api/conflicts/list_conflicts.md

@@ -0,0 +1,69 @@
+# List Conflicts
+
+List all sync conflicts for the current user.
+
+**Endpoint**: `GET /api/conflicts`
+**Auth**: Required
+
+## Query Parameters
+
+| Parameter | Type | Required | Description |
+|-----------|------|-----------|-------------|
+| status | string | No | Filter by status (active, resolved, dismissed) |
+| media_item_id | string (UUID) | No | Filter by media item |
+| limit | integer | No | Maximum number of conflicts to return (default: 50) |
+| offset | integer | No | Number of conflicts to skip (default: 0) |
+
+## Request Headers
+
+| Header | Type | Required | Description |
+|--------|------|-----------|-------------|
+| Authorization | string | Yes | Bearer token |
+
+### Example Request
+
+```http
+GET /api/conflicts?status=active&limit=10
+Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
+```
+
+## Response (200 OK)
+
+```json
+{
+  "conflicts": [
+    {
+      "id": "uuid",
+      "media_item_id": "book-uuid",
+      "media_item_title": "Sample Book",
+      "device_progress": {
+        "device_id": "device-uuid",
+        "device_name": "My Kobo",
+        "percentage": 75,
+        "position": 1234,
+        "updated_at": "2026-02-08T10:00:00Z"
+      },
+      "server_progress": {
+        "percentage": 50,
+        "position": 800,
+        "updated_at": "2026-02-08T09:00:00Z"
+      },
+      "status": "active",
+      "created_at": "2026-02-08T10:00:00Z"
+    }
+  ],
+  "total": 5,
+  "limit": 10,
+  "offset": 0
+}
+```
+
+## Error Responses
+
+| Code | Description |
+|------|-------------|
+| 401 | Invalid or expired token |
+
+## Try It Out
+
+<!-- API Explorer will be inserted here in Phase 3 -->