fix(render,store): frpc user 支持 + 修正 useEncryption/useCompression 渲染位置

- store.Remote 新增 user 字段（DB 列名 usr，避开保留字；migrate() 自动加列），
  渲染为 frpc 全局 user。面板型 frps（如 ChhChongGou 实例）强制要求 user 登录，
  缺失时服务端返回 panel authentication unavailable: panel HTTP status 403
- ★ 修复渲染 bug：useEncryption/useCompression/bandwidthLimit 必须内嵌在 proxy 的
  transport 对象（frpc ProxyTransport）。此前渲染在 proxy 顶层，frpc 默认
  --strict-config 直接拒载：unknown field "useEncryption"。任何启用加密/压缩
  的转发都无法启动。poolCount 无 proxy 级表达（官方 ProxyTransport 无此字段），
  保留在 store 但不再渲染
- 前端：RemoteNode 画布节点与 StatusView 表单加 user 输入（画布此前会静默
  清掉未声明的字段），带『面板型 frps 必填』提示
- 测试：user 往返（含迁移路径）、渲染含/不含 user、transport 内嵌与顶层
  非法键回归守卫

internal/store/store_test.go

@@ -58,3 +58,63 @@ func TestReplaceLinksClearsOld(t *testing.T) {
 		t.Fatalf("links = %+v", links)
 	}
 }
+
+// `usr` is a reserved SQL keyword in several dialects, so the remotes column is
+// named `usr`. This guards the mapping in both directions, including the
+// migrate() path that adds the column to pre-existing databases.
+func TestRemoteUserRoundTrip(t *testing.T) {
+	st, err := New(filepath.Join(t.TempDir(), "test.db"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer st.Close()
+
+	// A remote written without user (existing installs) must read back empty.
+	if err := st.UpsertRemote(Remote{Name: "plain", IP: "1.2.3.4", Port: 7000, Enabled: true}); err != nil {
+		t.Fatal(err)
+	}
+	if got, ok := st.GetRemote("plain"); !ok || got.User != "" {
+		t.Fatalf("plain remote user = %q ok=%v, want empty", got.User, ok)
+	}
+
+	want := Remote{Name: "panel", IP: "103.40.13.126", Port: 59999, Token: "tk", User: "e8f52adfaf0e5c95", Enabled: true}
+	if err := st.UpsertRemote(want); err != nil {
+		t.Fatal(err)
+	}
+	got, ok := st.GetRemote("panel")
+	if !ok || got.User != want.User {
+		t.Fatalf("user not persisted: %+v", got)
+	}
+	list, err := st.ListRemotes()
+	if err != nil {
+		t.Fatal(err)
+	}
+	var found bool
+	for _, r := range list {
+		if r.Name == "panel" {
+			found = true
+			if r.User != want.User {
+				t.Fatalf("ListRemotes user = %q, want %q", r.User, want.User)
+			}
+		}
+	}
+	if !found {
+		t.Fatal("panel remote missing from ListRemotes")
+	}
+
+	// Updating in place must not drop the column, and clearing it must work.
+	want.Token = "tk2"
+	if err := st.UpsertRemote(want); err != nil {
+		t.Fatal(err)
+	}
+	if got, _ := st.GetRemote("panel"); got.User != want.User || got.Token != "tk2" {
+		t.Fatalf("upsert lost fields: %+v", got)
+	}
+	want.User = ""
+	if err := st.UpsertRemote(want); err != nil {
+		t.Fatal(err)
+	}
+	if got, _ := st.GetRemote("panel"); got.User != "" {
+		t.Fatalf("user not cleared: %q", got.User)
+	}
+}