deploy: add bootstrap.sh + Caddyfile + systemd unit + demo pool

One-shot deploy for fresh Ubuntu 24.04 root SSH:
  curl -fsSL https://gitea.ahkhan.me/apps/quiz/raw/branch/master/deploy/bootstrap.sh | bash

bootstrap.sh: idempotent stage-by-stage installer for Caddy, Python venv,
quiz system user, repo clone to /opt/quiz, env-var prompts, systemd unit,
Caddyfile, and a healthz check. Reattaches /dev/tty so curl|bash can read
the admin password interactively.

quiz.service: uvicorn under the quiz system user (no shell, no SSH),
ProtectSystem=full, ProtectHome=true, PrivateTmp=true, NoNewPrivileges=true.

Caddyfile.tpl: reverse_proxy 127.0.0.1:8001 with auto Let's Encrypt;
DOMAIN substituted at install time.

examples/pool_example.json: generic demo pool, schema reference only.

README rewritten around the deploy flow + class-day lifecycle.

deploy/quiz.service

@@ -0,0 +1,21 @@
+[Unit]
+Description=Live in-lecture quiz portal (uvicorn)
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=quiz
+Group=quiz
+WorkingDirectory=/opt/quiz
+EnvironmentFile=/opt/quiz/.env
+ExecStart=/opt/quiz/.venv/bin/uvicorn app.main:app --host 127.0.0.1 --port 8001 --no-access-log
+Restart=on-failure
+RestartSec=2
+ProtectSystem=full
+ProtectHome=true
+PrivateTmp=true
+NoNewPrivileges=true
+
+[Install]
+WantedBy=multi-user.target