Phase 3 Week 7: Add KOReader routes, tests, and documentation

- Add KOReader sync endpoints to main application router
- Create Bruno API collection for testing KOReader endpoints
- Add integration tests for KOReader functionality
- Include comprehensive README with setup instructions
- Test coverage for progress, metadata, library, and bookmarks sync
- Part of Phase 3 KOReader Integration implementation

bruno/koreader/Sync Progress.bru

@@ -0,0 +1,42 @@
+meta {
+  name: KOReader Sync Progress
+  type: http
+  seq: 1
+}
+
+post {
+  url: {{baseUrl}}/api/sync/koreader/progress
+  body: json({
+    "library_id": null,
+    "books": [
+      {
+        "uuid": "{{book_uuid}}",
+        "title": "Test Book",
+        "authors": ["Test Author"],
+        "progress": 0.45,
+        "percentage": 0.45,
+        "last_read": "2026-01-30T20:00:00Z",
+        "chapter": 5,
+        "character": 15432,
+        "epubcfi": "epubcfi(/6/4/2:15)",
+        "page": 89,
+        "total_pages": 200
+      }
+    ],
+    "sync_mode": "immediate",
+    "device_info": {
+      "koreader_version": "2024.01",
+      "device_model": "kindle-paperwhite-5"
+    }
+  })
+  headers: {
+    Authorization: Bearer {{device_token}},
+    Content-Type: application/json
+  }
+}
+
+assert {
+  res.status == 202
+  res.body.sync_status == "accepted"
+  res.body.books_synced >= 0
+}