feat(web): vercel deployment and vds compose/systemd setup

Add Vercel config with React Router preset, vercel-build script and
/api/auth rewrite to the Convex site. Add VDS staging compose for the
Rivet engine and runner plus systemd units, deployment plan, and
Docker/Vercel ignore rules. Lockfile covers both the web and agents
dependency additions.

deploy/systemd/Caddyfile

@@ -0,0 +1,18 @@
+{
+	email ops@zopu.ai
+}
+{$AGENTS_HOST} {
+	encode zstd gzip
+
+	route {
+		reverse_proxy /agents/zopu/* 127.0.0.1:3000
+		reverse_proxy /internal/work-attempts/* 127.0.0.1:3000
+		reverse_proxy /api/rivet/* 127.0.0.1:3000
+		reverse_proxy /workflows/* 127.0.0.1:3000
+		reverse_proxy /health 127.0.0.1:3000
+		respond 404
+	}
+}
+:80 {
+	redir https://{host}{uri} permanent
+}