feat: add LanceDB vector database provider

- Implemented LanceDBProvider for managing vector collections, including methods for creating, deleting, and searching collections.
- Added support for LanceDB configuration in VectorDBConfig.
- Introduced stub for LanceDB provider when not built with the appropriate tag.
- Updated provider initialization to include LanceDB as a supported type.
- Created types and interfaces for vector operations, including Vector, SearchRequest, and SearchResult.
- Added tests for VectorDBConfig unmarshalling and for ensuring proper error handling when LanceDB is not built.
- Updated enums to include LanceDB type and labels.
- Modified frontend enums to reflect the addition of LanceDB.

internal/ai/rag/vectordb/lancedb_stub.go

@@ -0,0 +1,13 @@
+//go:build !lancedb
+
+package vectordb
+
+import (
+	"fmt"
+
+	"agent-desk/internal/pkg/config"
+)
+
+func NewLanceDBProvider(_ *config.LanceDBVectorDBConfig) (Provider, error) {
+	return nil, fmt.Errorf("LanceDB provider is not built. Rebuild with -tags lancedb and configure LanceDB native libraries")
+}