feat(deploy): serve SPA from server, Dockerfile, compose, deploy docs

- Add serveStatic middleware to server/src/app.ts to serve web/dist
- Include SPA fallback route for client-side routing deep links
- Create Dockerfile with multi-stage build (Node deps + build, slim runtime)
- Add docker-compose.yml for single-command deployment
- Add docs/deploy.md with deployment instructions and Caddy reverse proxy example
- Add bun run build:web step to CI pipeline after typecheck

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/src/app.ts

@@ -1,5 +1,6 @@
 import { Hono } from "hono";
 import { getCookie } from "hono/cookie";
+import { serveStatic } from "hono/bun";
 import type { Db } from "./db";
 import { authRoutes, isAuthenticated } from "./routes/auth";
 import { settingsRoutes } from "./routes/settings";
@@ -20,5 +21,7 @@ export function createApp(deps: Deps) {
   app.route("/api", authRoutes({ db: deps.db }));
   app.route("/api", settingsRoutes(deps));
   // Later route groups (connectors, chat) mount here.
+  app.use("/*", serveStatic({ root: "./web/dist" }));
+  app.get("/*", serveStatic({ path: "./web/dist/index.html" }));
   return app;
 }