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/bulk_dismiss_conflicts.md

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+# Bulk Dismiss Conflicts
+
+Dismiss multiple conflicts at once.
+
+**Endpoint**: `POST /api/conflicts/bulk-dismiss`
+**Auth**: Required
+**Content-Type**: `application/json`
+
+## Request Body
+
+| Field | Type | Required | Description |
+|--------|------|-----------|-------------|
+| conflict_ids | array of UUID | Yes | Array of conflict UUIDs to dismiss |
+
+### Example Request
+
+```json
+{
+  "conflict_ids": [
+    "550e8400-e29b-41d4-a716-446655440000",
+    "660e8400-e29b-41d4-a716-446655440001"
+  ]
+}
+```
+
+## Response (200 OK)
+
+```json
+{
+  "message": "Conflicts dismissed successfully",
+  "dismissed_count": 2
+}
+```
+
+## Error Responses
+
+| Code | Description |
+|------|-------------|
+| 400 | Invalid request body |
+| 401 | Invalid or expired token |
+
+## Try It Out
+
+<!-- API Explorer will be inserted here in Phase 3 -->

docs/developer/api/conflicts/bulk_resolve_conflicts.md

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+# Bulk Resolve Conflicts
+
+Resolve multiple conflicts at once using a specified strategy.
+
+**Endpoint**: `POST /api/conflicts/bulk-resolve`
+**Auth**: Required
+**Content-Type**: `application/json`
+
+## Request Body
+
+| Field | Type | Required | Description |
+|--------|------|-----------|-------------|
+| conflict_ids | array of UUID | Yes | Array of conflict UUIDs to resolve |
+| resolution | string | Yes | Resolution strategy: "device", "server", or "highest_progress" |
+
+### Example Request
+
+```json
+{
+  "conflict_ids": [
+    "550e8400-e29b-41d4-a716-446655440000",
+    "660e8400-e29b-41d4-a716-446655440001"
+  ],
+  "resolution": "highest_progress"
+}
+```
+
+## Response (200 OK)
+
+```json
+{
+  "message": "Conflicts resolved successfully",
+  "resolved_count": 2,
+  "failed_count": 0
+}
+```
+
+## Error Responses
+
+| Code | Description |
+|------|-------------|
+| 400 | Invalid request body |
+| 401 | Invalid or expired token |
+| 400 | Invalid resolution strategy |
+
+## Try It Out
+
+<!-- API Explorer will be inserted here in Phase 3 -->

docs/developer/api/conflicts/delete_conflict.md

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+# Delete Conflict
+
+Delete a specific conflict record.
+
+**Endpoint**: `DELETE /api/conflicts/:id`
+**Auth**: Required
+
+## Path Parameters
+
+| Parameter | Type | Required | Description |
+|-----------|------|-----------|-------------|
+| id | string (UUID) | Yes | Conflict UUID |
+
+## Request Headers
+
+| Header | Type | Required | Description |
+|--------|------|-----------|-------------|
+| Authorization | string | Yes | Bearer token |
+
+### Example Request
+
+```http
+DELETE /api/conflicts/550e8400-e29b-41d4-a716-446655440000
+Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
+```
+
+## Response (204 No Content)
+
+Conflict deleted successfully.
+
+## Error Responses
+
+| Code | Description |
+|------|-------------|
+| 401 | Invalid or expired token |
+| 404 | Conflict not found |
+
+## Try It Out
+
+<!-- API Explorer will be inserted here in Phase 3 -->

docs/developer/api/conflicts/dismiss_all_resolved.md

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+# Dismiss All Resolved
+
+Dismiss all resolved conflicts.
+
+**Endpoint**: `POST /api/conflicts/dismiss-all`
+**Auth**: Required
+
+## Request Headers
+
+| Header | Type | Required | Description |
+|--------|------|-----------|-------------|
+| Authorization | string | Yes | Bearer token |
+
+### Example Request
+
+```http
+POST /api/conflicts/dismiss-all
+Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
+```
+
+## Response (200 OK)
+
+```json
+{
+  "message": "All resolved conflicts dismissed",
+  "count": 15
+}
+```
+
+## Error Responses
+
+| Code | Description |
+|------|-------------|
+| 401 | Invalid or expired token |
+
+## Try It Out
+
+<!-- API Explorer will be inserted here in Phase 3 -->

docs/developer/api/conflicts/get_conflict.md

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+# Get Conflict Details
+
+Get detailed information about a specific conflict.
+
+**Endpoint**: `GET /api/conflicts/:id`
+**Auth**: Required
+
+## Path Parameters
+
+| Parameter | Type | Required | Description |
+|-----------|------|-----------|-------------|
+| id | string (UUID) | Yes | Conflict UUID |
+
+## Request Headers
+
+| Header | Type | Required | Description |
+|--------|------|-----------|-------------|
+| Authorization | string | Yes | Bearer token |
+
+### Example Request
+
+```http
+GET /api/conflicts/550e8400-e29b-41d4-a716-446655440000
+Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
+```
+
+## Response (200 OK)
+
+```json
+{
+  "id": "uuid",
+  "media_item": {
+    "id": "book-uuid",
+    "title": "Sample Book",
+    "authors": ["Author Name"]
+  },
+  "device_progress": {
+    "device_id": "device-uuid",
+    "device_name": "My Kobo",
+    "percentage": 75,
+    "position": 1234,
+    "page": 150,
+    "updated_at": "2026-02-08T10:00:00Z"
+  },
+  "server_progress": {
+    "percentage": 50,
+    "position": 800,
+    "page": 100,
+    "updated_at": "2026-02-08T09:00:00Z"
+  },
+  "device_bookmarks": [
+    {
+      "position": 1234,
+      "text": "Interesting passage",
+      "created_at": "2026-02-08T10:00:00Z"
+    }
+  ],
+  "server_bookmarks": [
+    {
+      "position": 800,
+      "text": "Another passage",
+      "created_at": "2026-02-07T15:00:00Z"
+    }
+  ],
+  "status": "active",
+  "created_at": "2026-02-08T10:00:00Z"
+}
+```
+
+## Error Responses
+
+| Code | Description |
+|------|-------------|
+| 401 | Invalid or expired token |
+| 404 | Conflict not found |
+
+## Try It Out
+
+<!-- API Explorer will be inserted here in Phase 3 -->

docs/developer/api/conflicts/list_conflicts.md

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+# 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 -->

docs/developer/api/conflicts/resolve_conflict.md

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+# Resolve Conflict
+
+Resolve a specific conflict by choosing which version to keep.
+
+**Endpoint**: `POST /api/conflicts/:id/resolve`
+**Auth**: Required
+**Content-Type**: `application/json`
+
+## Path Parameters
+
+| Parameter | Type | Required | Description |
+|-----------|------|-----------|-------------|
+| id | string (UUID) | Yes | Conflict UUID |
+
+## Request Body
+
+| Field | Type | Required | Description |
+|--------|------|-----------|-------------|
+| resolution | string | Yes | Resolution strategy: "device", "server", or "highest_progress" |
+
+### Example Request
+
+```json
+{
+  "resolution": "device"
+}
+```
+
+## Response (200 OK)
+
+```json
+{
+  "message": "Conflict resolved successfully",
+  "conflict_id": "uuid",
+  "resolution": "device"
+}
+```
+
+## Error Responses
+
+| Code | Description |
+|------|-------------|
+| 400 | Invalid resolution strategy |
+| 401 | Invalid or expired token |
+| 404 | Conflict not found |
+| 400 | Conflict already resolved |
+
+## Try It Out
+
+<!-- API Explorer will be inserted here in Phase 3 -->