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/adapters/display-terminal/src/lib.rs

@@ -1,5 +1,6 @@
 use client_domain::{BoundingBox, DisplayPort};
 
+#[derive(Default)]
 pub struct TerminalDisplay;
 
 impl TerminalDisplay {
@@ -12,12 +13,24 @@ impl DisplayPort for TerminalDisplay {
     type Error = std::io::Error;
 
     fn clear_region(&mut self, bounds: BoundingBox) -> Result<(), Self::Error> {
-        println!("[CLEAR] ({}, {}) {}x{}", bounds.x, bounds.y, bounds.width, bounds.height);
+        println!(
+            "[CLEAR] ({}, {}) {}x{}",
+            bounds.x, bounds.y, bounds.width, bounds.height
+        );
         Ok(())
     }
 
-    fn draw_text(&mut self, text: &str, x: u16, y: u16, bounds: BoundingBox) -> Result<(), Self::Error> {
-        println!("[TEXT]  ({x}, {y}) in {}x{}: \"{text}\"", bounds.width, bounds.height);
+    fn draw_text(
+        &mut self,
+        text: &str,
+        x: u16,
+        y: u16,
+        bounds: BoundingBox,
+    ) -> Result<(), Self::Error> {
+        println!(
+            "[TEXT]  ({x}, {y}) in {}x{}: \"{text}\"",
+            bounds.width, bounds.height
+        );
         Ok(())
     }
 
@@ -27,7 +40,10 @@ impl DisplayPort for TerminalDisplay {
     }
 
     fn fill_background(&mut self, bounds: BoundingBox) -> Result<(), Self::Error> {
-        println!("[BG]   ({}, {}) {}x{}", bounds.x, bounds.y, bounds.width, bounds.height);
+        println!(
+            "[BG]   ({}, {}) {}x{}",
+            bounds.x, bounds.y, bounds.width, bounds.height
+        );
         Ok(())
     }