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/provider_test.go

@@ -0,0 +1,23 @@
+package vectordb
+
+import (
+	"strings"
+	"testing"
+
+	"agent-desk/internal/pkg/config"
+)
+
+func TestInitLanceDBWithoutBuildTagReturnsActionableError(t *testing.T) {
+	err := Init(&config.VectorDBConfig{
+		Type: "lancedb",
+		LanceDB: config.LanceDBVectorDBConfig{
+			Path: "data/lancedb",
+		},
+	})
+	if err == nil {
+		t.Fatal("Init(lancedb) error = nil, want actionable build tag error")
+	}
+	if !strings.Contains(err.Error(), "LanceDB provider is not built") {
+		t.Fatalf("Init(lancedb) error = %q, want build tag guidance", err.Error())
+	}
+}