add SPA config UI, wire media/rss adapters, event-driven layout push

- React SPA: dashboard, data sources CRUD, widgets CRUD, layout builder,
  presets. TanStack Router + Query, shadcn/ui, Vite proxy to :3000
- wire media + rss adapters into polling loop, remove xtb source type
- media adapter: read username/password from headers, proper subsonic auth
- event handler: subscribe to LayoutChanged, push screen update to clients
- fix clippy warnings across workspace (Default impls, collapsible ifs,
  redundant closures, is_none_or, unused imports)

crates/client-application/src/client_app.rs

@@ -1,9 +1,7 @@
-use std::collections::HashMap;
-use domain::LayoutNode;
 use client_domain::{BoundingBox, LayoutEngine, RenderTree};
-use protocol::{
-    ServerMessage, WidgetDescriptor, WireDisplayHint, WireWidgetState, WireLayoutNode,
-};
+use domain::LayoutNode;
+use protocol::{ServerMessage, WidgetDescriptor, WireDisplayHint, WireLayoutNode, WireWidgetState};
+use std::collections::HashMap;
 
 pub struct ClientApp {
     screen: BoundingBox,
@@ -33,9 +31,7 @@ impl ClientApp {
             ServerMessage::ScreenUpdate { layout, widgets } => {
                 self.handle_screen_update(layout, widgets)
             }
-            ServerMessage::DataUpdate { widgets } => {
-                self.handle_data_update(widgets)
-            }
+            ServerMessage::DataUpdate { widgets } => self.handle_data_update(widgets),
             ServerMessage::Heartbeat => Vec::new(),
         }
     }
@@ -50,7 +46,8 @@ impl ClientApp {
 
         self.widget_states.clear();
         for w in &widgets {
-            self.widget_states.insert(w.id, (w.display_hint.clone(), w.state.clone()));
+            self.widget_states
+                .insert(w.id, (w.display_hint.clone(), w.state.clone()));
         }
 
         let repaints = self.build_repaints_for_all(&new_tree);
@@ -58,10 +55,7 @@ impl ClientApp {
         repaints
     }
 
-    fn handle_data_update(
-        &mut self,
-        widgets: Vec<WidgetDescriptor>,
-    ) -> Vec<RepaintCommand> {
+    fn handle_data_update(&mut self, widgets: Vec<WidgetDescriptor>) -> Vec<RepaintCommand> {
         let tree = match &self.render_tree {
             Some(t) => t,
             None => return Vec::new(),
@@ -70,9 +64,10 @@ impl ClientApp {
         let mut repaints = Vec::new();
 
         for w in widgets {
-            let changed = self.widget_states
+            let changed = self
+                .widget_states
                 .get(&w.id)
-                .map_or(true, |(_, prev_state)| *prev_state != w.state);
+                .is_none_or(|(_, prev_state)| *prev_state != w.state);
 
             if changed {
                 if let Some(bounds) = tree.get_widget_bounds(w.id) {