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/tcp-client/src/lib.rs

@@ -1,8 +1,8 @@
+use client_domain::NetworkPort;
+use protocol::MAX_FRAME_SIZE;
 use std::io::{Read, Write};
 use std::net::TcpStream;
 use std::time::Duration;
-use client_domain::NetworkPort;
-use protocol::MAX_FRAME_SIZE;
 
 #[derive(Debug, thiserror::Error)]
 pub enum TcpClientError {
@@ -14,13 +14,14 @@ pub enum TcpClientError {
     FrameTooLarge(usize),
 }
 
+#[derive(Default)]
 pub struct StdTcpClient {
     stream: Option<TcpStream>,
 }
 
 impl StdTcpClient {
     pub fn new() -> Self {
-        Self { stream: None }
+        Self::default()
     }
 }
 
@@ -30,7 +31,9 @@ impl NetworkPort for StdTcpClient {
     fn connect(&mut self, addr: &str) -> Result<(), Self::Error> {
         let stream = TcpStream::connect(addr).map_err(TcpClientError::Io)?;
         stream.set_nonblocking(true).map_err(TcpClientError::Io)?;
-        stream.set_read_timeout(Some(Duration::from_millis(10))).map_err(TcpClientError::Io)?;
+        stream
+            .set_read_timeout(Some(Duration::from_millis(10)))
+            .map_err(TcpClientError::Io)?;
         self.stream = Some(stream);
         Ok(())
     }
@@ -63,7 +66,9 @@ impl NetworkPort for StdTcpClient {
 
         let mut payload = vec![0u8; len];
         stream.set_nonblocking(false).map_err(TcpClientError::Io)?;
-        stream.read_exact(&mut payload).map_err(TcpClientError::Io)?;
+        stream
+            .read_exact(&mut payload)
+            .map_err(TcpClientError::Io)?;
         stream.set_nonblocking(true).map_err(TcpClientError::Io)?;
 
         Ok(Some(payload))