Add option to disable frontend

crates/frontend/src/config.rs

@@ -1,9 +1,15 @@
 use serde::{Deserialize, Serialize};
 
+fn default_enabled() -> bool {
+    true
+}
+
 #[derive(Deserialize, Serialize, Debug, Clone)]
 #[serde(deny_unknown_fields)]
 pub struct FrontendConfig {
     #[serde(serialize_with = "hex::serde::serialize")]
     #[serde(deserialize_with = "hex::serde::deserialize")]
     pub secret_key: [u8; 64],
+    #[serde(default = "default_enabled")]
+    pub enabled: bool,
 }