Go: Add admin server status checking (#13571)

### What problem does this PR solve?

RAGFlow server isn't available when admin server isn't connected.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

build.sh

@@ -92,7 +92,8 @@ build_go() {
     
     echo "Building Go binary: $OUTPUT_BINARY"
     GOPROXY=${GOPROXY:-https://goproxy.cn,https://proxy.golang.org,direct} CGO_ENABLED=1 go build -o "$OUTPUT_BINARY" ./cmd/server_main.go
-    
+    GOPROXY=${GOPROXY:-https://goproxy.cn,https://proxy.golang.org,direct} CGO_ENABLED=1 go build -o "$OUTPUT_BINARY" ./cmd/admin_server.go
+
     if [ ! -f "$OUTPUT_BINARY" ]; then
         echo -e "${RED}Error: Failed to build Go binary${NC}"
         exit 1