Resolves#75
### Description
This pull request implements a smart, Native AOT-compliant contextual recommendation engine for the desktop dashboard to drive user retention and cross-book monetization.
### Key Changes
1. **Application Layer**:
- Declared `IUserReadingStateStore` interface to decouple reading state discovery.
- Added `IVectorSearchStore.SearchGlobalExcludeAsync(...)` to abstract semantic similarity searches with exclusions.
- Defined `GetContextualRecommendationsQuery` and response DTOs (`ContextualRecommendationResponse`, `RecommendationDto`).
2. **Infrastructure Layer**:
- Implemented `UserReadingStateStore` using EF Core with DbContext pooling.
- Implemented `SearchGlobalExcludeAsync` in `VectorSearchStore` to construct gRPC Qdrant filters (excluding the active book ID) and fetch `bookTitle` and `chapterTitle` from point payloads.
- Implemented `GetContextualRecommendationsQueryHandler` using clean abstractions.
3. **Web & Serialization Layer**:
- Mapped `GET /api/recommendations` endpoint.
- Registered types in `AppJsonContext.cs` for AOT-compliant JSON serialization.
4. **Verification**:
- Added complete unit test coverage in `GetContextualRecommendationsQueryTests.cs`. All 30 unit tests pass.
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Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Reviewed-on: #76
Co-authored-by: Antigravity <antigravity@google.com>
Co-committed-by: Antigravity <antigravity@google.com>
Antigravity
1d6862016d