Refresh login screen with server list UI and refactor platform config

Redesign login view with server card list, add/edit/delete modals,
and per-server ping status display. Rename ProxyOverrides to ClientConfig,
remove ConfigSystemInterface in favor of direct platform methods
(load_config, load_username, set_default_username, load_server_url),
remove SharedState threading in favor of global STATE, simplify
network_loop and audio setup, update proxy endpoint from /overrides
to /config, and clean up desktop launch configuration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

gui/src/imp/stub.rs

@@ -1,16 +1,15 @@
 /// Stub implementation of the platform interface, so that we can
 /// `cargo check` without any --feature flags.
-use crate::{app::SharedState, effects::AudioProcessor};
+use crate::effects::AudioProcessor;
 use color_eyre::eyre::Error;
 use dioxus::hooks::UnboundedReceiver;
-use mumble_web2_common::{ProxyOverrides, ServerEntry, ServerStatus};
+use mumble_web2_common::{ClientConfig, ServerEntry, ServerStatus};
 use std::future::Future;
 
 pub struct StubPlatform;
 
 impl super::PlatformInterface for StubPlatform {
     type AudioSystem = StubAudioSystem;
-    type ConfigSystem = StubConfigSystem;
 
     fn init_logging() {
         panic!("stubbed platform")
@@ -24,8 +23,7 @@ impl super::PlatformInterface for StubPlatform {
         _address: String,
         _username: String,
         _event_rx: &mut UnboundedReceiver<crate::app::Command>,
-        _overrides: &ProxyOverrides,
-        _state: SharedState,
+        _gui_config: &ClientConfig,
     ) -> impl Future<Output = Result<(), Error>> {
         async { panic!("stubbed platform") }
     }
@@ -43,10 +41,22 @@ impl super::PlatformInterface for StubPlatform {
         async { panic!("stubbed platform") }
     }
 
-    fn load_proxy_overrides() -> impl Future<Output = color_eyre::Result<ProxyOverrides>> {
+    fn load_config() -> impl Future<Output = color_eyre::Result<ClientConfig>> {
         async { panic!("stubbed platform") }
     }
 
+    fn load_username() -> Option<String> {
+        panic!("stubbed platform")
+    }
+
+    fn load_server_url() -> Option<String> {
+        panic!("stubbed platform")
+    }
+
+    fn set_default_username(_username: &str) -> Option<()> {
+        panic!("stubbed platform")
+    }
+
     fn set_default_server(_server: &str) -> Option<()> {
         panic!("stubbed platform")
     }
@@ -97,29 +107,6 @@ impl super::AudioPlayerInterface for StubAudioPlayer {
     }
 }
 
-#[derive(Clone)]
-pub struct StubConfigSystem;
-
-impl super::ConfigSystemInterface for StubConfigSystem {
-    fn new() -> Result<Self, Error> {
-        panic!("stubbed platform")
-    }
-
-    fn config_get<T>(&self, key: &str) -> Option<T>
-    where
-        T: serde::de::DeserializeOwned,
-    {
-        panic!("stubbed platform")
-    }
-
-    fn config_set<T>(&self, key: &str, value: &T)
-    where
-        T: serde::Serialize,
-    {
-        panic!("stubbed platform")
-    }
-}
-
 #[allow(unused)]
 pub struct SpawnHandle;