feat(intelligence): implement global hybrid search engine and monetization logic

- Created IUserLibraryStore and IVectorSearchStore abstractions to decouple relational DB and Qdrant gRPC logic from Application Layer
- Implemented MediatR GetGlobalIntelligenceQuery with value-first teaser RAG monetization logic
- Registered new request and response DTOs in AppJsonContext for Native AOT source-generated serialization
- Bound RagMonetizationOptions via IOptions pattern in appsettings.json configuration
- Added POST /api/intelligence endpoint on server and implemented GetGlobalIntelligenceAsync in WASM client service
- Refactored Intelligence.razor to consume the backend-driven global hybrid search Q&A engine

src/NexusReader.Web/appsettings.Test.json

@@ -9,5 +9,10 @@
     "AllowRegistration": false,
     "AllowPasswordReset": false
   },
+  "RagMonetization": {
+    "BaselineThreshold": 0.45,
+    "DeltaThreshold": 0.15,
+    "UpgradeThreshold": 0.70
+  },
   "ApiBaseUrl": "http://localhost:5104"
 }