Implement Create/Drop Index/Metadata index in GO (#13791)

### What problem does this PR solve?

Implement Create/Drop Index/Metadata index in GO

New API handling in GO:
POST/kb/index 
DELETE /kb/index
POST /tenant/doc_meta_index
DELETE /tenant/doc_meta_index

CREATE INDEX FOR DATASET 'dataset_name' VECTOR_SIZE 1024;
DROP INDEX FOR DATASET 'dataset_name';
CREATE INDEX DOC_META;
DROP INDEX DOC_META;

### Type of change

- [x] Refactoring

internal/utility/path.go

@@ -0,0 +1,46 @@
+/*
+Copyright 2026 The InfiniFlow Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package utility
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+)
+
+// GetProjectRoot returns the project root directory by finding go.mod marker
+func GetProjectRoot() string {
+	// Try environment variable first
+	if confDir := os.Getenv("RAGFLOW_CONF_DIR"); confDir != "" {
+		return confDir
+	}
+
+	// Find project root by looking for go.mod
+	_, curFile, _, _ := runtime.Caller(0)
+	dir := filepath.Dir(curFile)
+	for {
+		if _, err := os.Stat(filepath.Join(dir, "go.mod")); err == nil {
+			return dir
+		}
+		parent := filepath.Dir(dir)
+		if parent == dir {
+			// Reached filesystem root, fallback to hardcoded path
+			return filepath.Dir(filepath.Dir(filepath.Dir(filepath.Dir(curFile))))
+		}
+		dir = parent
+	}
+}