Run Freezmo as a systemd user service

After a reboot the app was simply gone because it only ever ran as a
foreground `npm start`. deploy/freezmo.service runs the production build
under systemd (user), restarts on crash and starts at boot:

- ExecStart runs next start directly (no npm wrapper), 0.0.0.0:3207.
- AssertPathExists=.next/BUILD_ID refuses to start without a build.
- After/Wants network-online, and After=ollama.service for local mode.
- README: install steps, useful commands, and the stop-build-start
  sequence for manual rebuilds (build and running server share .next/).

Installed and verified locally: enabled in default.target.wants with
linger already on, active after a stop/start cycle, 200 on
127.0.0.1:3207 and the LAN IP, and it self-heals after a kill -9.

deploy/freezmo.service

@@ -0,0 +1,33 @@
+[Unit]
+# Freezmo — self-hosted notes-to-study-feed app.
+# Install (per user, no root needed):
+#   mkdir -p ~/.config/systemd/user
+#   cp deploy/freezmo.service ~/.config/systemd/user/
+#   systemctl --user daemon-reload
+#   systemctl --user enable --now freezmo.service
+#   loginctl enable-linger "$USER"     # start at boot without logging in
+# Logs:  journalctl --user -u freezmo -f
+Description=Freezmo (self-hosted study app)
+Documentation=file://%h/freezmo/README.md
+After=network-online.target
+Wants=network-online.target
+# In OLLAMA_AUTH=local mode the daemon should be up first (no-op otherwise).
+After=ollama.service
+
+[Service]
+Type=simple
+WorkingDirectory=%h/freezmo
+Environment=NODE_ENV=production
+Environment=NEXT_TELEMETRY_DISABLED=1
+Environment=PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+# Refuse to start without a production build — clearer than next crashing in a
+# restart loop. Run `npm run build` in %h/freezmo first.
+AssertPathExists=%h/freezmo/.next/BUILD_ID
+# Next.js loads .env.local (OLLAMA_*) from the working directory itself.
+ExecStart=/bin/node %h/freezmo/node_modules/next/dist/bin/next start -H 0.0.0.0 -p 3207
+Restart=always
+RestartSec=3
+TimeoutStartSec=0
+
+[Install]
+WantedBy=default.target