Refactor Qdrant architecture for reusability and maintainability

[google-labs-jules]

Refactored the Qdrant client usage to eliminate code duplication and scattered configuration.
Created a new utils/qdrant directory with the following modules:

• client.py: Singleton QdrantClientManager.
• config.py: Centralized collection and vector configuration.
• embeddings.py: EmbeddingService for unified model management and caching.
• operations.py: QdrantOperations abstraction for common CRUD and search operations.
• filters.py: FilterBuilder for constructing complex Qdrant filters.

Updated existing files to use these new modules:

• utils/knowledge_base/qdrant_retrieval.py
• utils/knowledge_base/memory_retrieval.py
• utils/knowledge_base/loadvector_qdrant.py
• api/embeddings.py

This refactoring improves maintainability, connection pooling, and error handling consistency across the application.

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PR created automatically by Jules for task 8790263781290474851 started by @NguyenNhat4

[google-labs-jules]

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