feat(hub): show "update available" notification in hub web UI (#1830)

* refactor, make opt-in, and deprecate /api/beszel/getkey in favor of /api/beszel/info

---------

Co-authored-by: henrygd <hank@henrygd.me>

internal/hub/hub_test.go

@@ -606,6 +606,17 @@ func TestApiRoutesAuthentication(t *testing.T) {
 			ExpectedContent: []string{"\"key\":", "\"v\":"},
 			TestAppFactory:  testAppFactory,
 		},
+		{
+			Name:   "GET /info - should return the same as /getkey",
+			Method: http.MethodGet,
+			URL:    "/api/beszel/info",
+			Headers: map[string]string{
+				"Authorization": userToken,
+			},
+			ExpectedStatus:  200,
+			ExpectedContent: []string{"\"key\":", "\"v\":"},
+			TestAppFactory:  testAppFactory,
+		},
 		{
 			Name:            "GET /first-run - no auth should succeed",
 			Method:          http.MethodGet,