Phase 8: Production deployment (Debian 13, Nginx Proxy Manager)

Deployment artifacts for the two-server architecture from ARCHITECTURE.md
§9, grounded in verified Debian 13 (trixie) package facts (Python 3.13,
PostgreSQL 17, Node.js 20, redis-server 8.0, certbot 4.0, ufw --
confirmed rather than guessed) rather than a generic "modern Linux" guide:
deploy/systemd/chatapp.service, deploy/chatapp.env.example,
deploy/backup-postgres.sh, deploy/upgrade.sh, and DEPLOYMENT.md as the
actual numbered runbook.

Revised mid-implementation once the user clarified the app sits behind an
existing, separate Nginx Proxy Manager rather than local Nginx+certbot:
dropped the local Nginx config entirely, gunicorn now binds a TCP port
instead of a Unix socket, and app/main.py gained a static-file mount + SPA
fallback route so gunicorn alone serves the built frontend, /api, and /ws
on one port -- what lets NPM's simple one-upstream-per-domain mode work
with zero custom path routing. Path-traversal-guarded (full_path comes
straight from the URL) and cache-header-differentiated (far-future
immutable on Vite's content-hashed assets, no-cache on index.html/sw.js/
manifest so a deploy actually propagates instead of leaving clients on a
stale service worker) -- verified locally against a real gunicorn process
serving a real frontend build, not just eyeballed.

Two real gaps found and fixed alongside the docs, not just noted: gunicorn
wasn't a dependency anywhere despite being the whole app-server design, and
there was no WebSocket reconnect logic on the client -- a reverse proxy's
idle-connection timeout (NPM's or otherwise) would have silently killed a
quiet chat connection with nothing to recover it. Added exponential-backoff
reconnect to useChatSocket.ts, verified by hand (killed and restarted the
local dev backend mid-session, confirmed auto-reconnect and that a message
sends successfully afterward with no page reload).

Every command in DEPLOYMENT.md that could be verified locally, was: the
exact systemd ExecStart line run against local dev Postgres/Redis with
clean SIGTERM shutdown, the static-file serving behavior against a real
build, both shell scripts syntax-checked. What couldn't be verified from
this sandbox (actual Debian 13 hardware, Nginx Proxy Manager itself) is
flagged explicitly in the plan rather than claimed.

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

deploy/backup-postgres.sh

@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+# Nightly Postgres backup for the KeepItTalking data server.
+#
+# Install (as root, on the data server):
+#   sudo cp deploy/backup-postgres.sh /usr/local/bin/chatapp-backup-postgres.sh
+#   sudo chmod 0700 /usr/local/bin/chatapp-backup-postgres.sh
+#   sudo crontab -e
+#     # add:
+#     0 3 * * * /usr/local/bin/chatapp-backup-postgres.sh
+#
+# See ../DEPLOYMENT.md for the full data-server setup this fits into.
+
+set -euo pipefail
+
+DB_NAME="chatapp"
+DB_USER="chatapp"
+BACKUP_DIR="/var/backups/chatapp"
+RETENTION_DAYS=14
+TIMESTAMP="$(date +%F-%H%M%S)"
+DEST="${BACKUP_DIR}/chatapp-${TIMESTAMP}.sql.gz"
+
+mkdir -p "$BACKUP_DIR"
+
+# Runs as the postgres OS user (peer auth) so no password handling here --
+# see DEPLOYMENT.md for why the crontab entry above is on root's crontab
+# calling `sudo -u postgres` implicitly via pg_dump's own permission model.
+sudo -u postgres pg_dump --format=plain --no-owner --dbname="$DB_NAME" \
+  | gzip > "$DEST"
+
+echo "Backed up ${DB_NAME} to ${DEST}"
+
+# Local rotation -- keep RETENTION_DAYS days on this box regardless of
+# whether off-box shipping (below) is configured yet.
+find "$BACKUP_DIR" -name 'chatapp-*.sql.gz' -mtime "+${RETENTION_DAYS}" -delete
+
+# --- Off-box shipping -------------------------------------------------
+# Not configured yet -- destination wasn't decided as of this script being
+# written. Uncomment and fill in ONE of these once you have somewhere to
+# send it; a local-only backup doesn't survive losing this machine.
+#
+# rsync (to a second host reachable by the data server, e.g. over the same
+# private network / a WireGuard tunnel used for anything else):
+#   rsync -a "$DEST" backup-user@backup-host:/path/to/chatapp-backups/
+#
+# S3-compatible object storage (needs `aws configure` or rclone set up
+# separately first):
+#   aws s3 cp "$DEST" s3://your-bucket/chatapp-backups/
+#   # or: rclone copy "$DEST" remote:chatapp-backups/