Add terminal client, memory, model fallback, version and install improvements

- codecraft: full-screen terminal client (ratatui) – local tools and files,
  models via the CodeCraft server gateway or own providers (standalone with a
  guided setup), slash commands, @files, permission dialogs, resume, update
- Static Linux CLI builds (x86_64/aarch64, cargo-zigbuild) served by the
  server: /cli/install.sh and /cli/download/<target>
- Project memory (remember tool, .codecraft/memory.md) and personal memory
- Model fallback when a host is unreachable or a budget is used up
- Version/commit in UI and health, daily release check, "What's new" dialog
- PWA: install button, maskable icon, manifest id and screenshots
- Case-insensitive detection of connection errors for retries

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/main.rs

@@ -29,6 +29,7 @@ mod store;
 mod terminal;
 mod tools;
 mod types;
+mod update;
 
 use anyhow::Result;
 use tracing_subscriber::EnvFilter;
@@ -55,6 +56,7 @@ async fn main() -> Result<()> {
     push::spawn_listener(app.clone());
     terminal::spawn_reaper(app.clone());
     jobs::spawn_scheduler(app.clone());
+    update::spawn_checker(app.clone());
     let router = api::router(app);
     let listener = tokio::net::TcpListener::bind(&bind).await?;
     tracing::info!("listening on http://{bind}");