S5: WebSocket real-time — per-channel broadcast, auto-reconnect

Backend:
- AppState with per-channel broadcast::Sender map
- WS handler: auth via first message, keepalive pings, broadcast forwarding
- post_message broadcasts WsEvent::Message to all subscribers

Frontend:
- useChannelSocket hook: connects, auths, appends messages, auto-reconnects
- Removed 3s polling — WebSocket is primary, initial load via REST
- Deduplication on WS messages (sender also fetches after post)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/colony/src/main.rs

@@ -1,8 +1,11 @@
 mod db;
 mod routes;
+mod state;
+mod ws;
 
 use axum::{routing::get, Router};
 use sqlx::sqlite::SqlitePoolOptions;
+use state::AppState;
 use std::env;
 use tower_http::services::{ServeDir, ServeFile};
 
@@ -19,18 +22,18 @@ async fn main() {
 
     eprintln!("colony: connected to {}", db_url);
 
-    // Enable WAL mode
     sqlx::query("PRAGMA journal_mode=WAL")
         .execute(&pool)
         .await
         .unwrap();
 
-    // Run embedded migrations
     sqlx::migrate!("./migrations")
         .run(&pool)
         .await
         .expect("Failed to run migrations");
 
+    let state = AppState::new(pool);
+
     eprintln!("colony: migrations done, starting on port {}", port);
 
     let app = Router::new()
@@ -46,11 +49,11 @@ async fn main() {
             "/api/channels/{channel_id}/messages",
             get(routes::list_messages).post(routes::post_message),
         )
-        // Serve frontend static files, fallback to index.html for SPA routing
+        .route("/ws/{channel_id}", get(ws::ws_handler))
         .fallback_service(
             ServeDir::new("static").fallback(ServeFile::new("static/index.html")),
         )
-        .with_state(pool);
+        .with_state(state);
 
     let listener = tokio::net::TcpListener::bind(format!("0.0.0.0:{}", port))
         .await