feat(packaging/web): bundle the web console into the apt install (punktfunk-web)

Every user needs the console for pairing, so ship it via apt, auto-wired to the
host — no manual bun/env setup. New punktfunk-web .deb (Architecture: all,
Depends: nodejs >= 20 — runs the node-server build under apt-native node, no
bundled bun):

- packaging/debian/build-web-deb.sh: stages web/.output (server + public) + a
  /usr/bin/punktfunk-web-server wrapper (node) + the systemd --user units + the
  web.env template + docs. Refuses a bun bundle (Bun.serve) as a wrong-preset guard.
- scripts/punktfunk-web.service: --user unit on :3000, EnvironmentFile sources the
  host's ~/.config/punktfunk/mgmt-token (the shared bearer) + the generated
  web-password; sets PUNKTFUNK_MGMT_URL=https://127.0.0.1:47990 +
  NODE_TLS_REJECT_UNAUTHORIZED=0 (loopback self-signed cert). Restart=on-failure
  rides out the host-writes-token-first ordering.
- scripts/punktfunk-web-init.service + web-init.sh: --user one-shot that generates
  the login password (a .deb postinst runs as root → wrong $HOME) and surfaces it
  to the journal.
- build-deb.sh: punktfunk-host now Recommends punktfunk-web (apt pulls it by
  default; headless boxes opt out with --no-install-recommends).
- deb.yml: build the web console + smoke-boot it under node (gate the .deb on a
  real /login 200) + build-web-deb.sh; the publish loop globs it automatically.
- web/{.env.example,web.env.example}: document the auto-wiring vs a manual deploy.

End state: `apt install punktfunk-host` pulls punktfunk-web; enable both --user
services; the console logs in (password from the journal) and proxies the host's
HTTPS mgmt API with the shared token — zero hand-edited env. Local .deb build +
node smoke-boot verified.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/punktfunk-web-init.service

@@ -0,0 +1,17 @@
+# punktfunk web console first-run setup — systemd USER one-shot.
+#
+# Generates the console login password (PUNKTFUNK_UI_PASSWORD) in the streaming user's
+# ~/.config/punktfunk on first start, surfaced to the --user journal for retrieval. A .deb postinst
+# runs as root (wrong $HOME), so credential generation must happen as the user — hence this unit.
+# Pulled in by punktfunk-web.service (Wants=); also runnable directly.
+[Unit]
+Description=punktfunk web console first-run setup (login password)
+ConditionPathExists=!%h/.config/punktfunk/web-password
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/usr/share/punktfunk-web/web-init.sh
+
+[Install]
+WantedBy=default.target