feat(appgate): apps with their own login can skip the node login

Some apps carry a complete account system and are broken by an upstream
challenge: git clients speak basic-auth (not browser cookies), and a
BTCPay checkout link handed to a customer must open for that customer.
Both were behind the gate's login page — the "non-browser clients need an
access token" gap disclosed in five consecutive releases.

- New manifest port policy `auth: open`: the daemon still fronts the port
  exactly like `gated` (loopback pin, external binds, frame-header fixes,
  app-down retry page, Tor upstream) but serves it without the login
  challenge. Requires auth_rationale, same burden of proof as `none`.
  Gitea 3001 and BTCPay 23000 declare it.
- Runtime operator override per app (security.set-app-gate → app-configs/
  <id>.json "gateEnabled"), surfaced as Settings → app → Access control.
  Wins over the manifest in both directions and applies on the next
  request — no restart, and it works today on catalog-covered apps whose
  signed manifest still says `gated`.
- The gate resolves policy per-request from the live port map, so a
  toggle takes effect without waiting for the 60s rebind sweep. "Off"
  never releases the port: gated apps are loopback-pinned, so releasing
  would strand them, not open them.
- security.app-gate-status now reports gate_enabled + any override.
- New guard test pins the `auth: open` set (both entries reviewed); the
  `auth: none` count moves 25 → 26, absorbing pre-existing drift from the
  phoenixd onboarding (loopback JSON API with its own generated password).
- Docs: the manifest spec's ports row documented only host/container/
  protocol — bind, auth, auth_rationale and session_passthrough were
  undocumented. Added a full "Ports & the app gate" section plus a
  developer-guide entry telling app authors to enforce their own auth
  regardless, since the operator can flip the gate either way.

Verified live on archi-dev-box from an external address: gated → 401 gate
page; override off → Gitea 200 own page, BTCPay 302 to its own login,
git-over-HTTP info/refs 200; override on → 401 again; clear → default.

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

docs/app-developer-guide.md

@@ -152,6 +152,21 @@ know the mechanics:
   policy, only its framing policy. You do not need a bespoke reverse proxy,
   header patches, or app config to be embeddable.
 
+### Apps with their own login: `auth: open`
+
+If your app carries a complete account system of its own — and especially if
+non-browser clients must reach it (git over HTTP, mobile apps, payment
+webhooks) — declare its gated port `auth: open` with an `auth_rationale`
+instead of `auth: gated`. The daemon still fronts the port exactly like a
+gated one (loopback pin, external binds, frame-header fixes, retry page,
+Tor onion), but serves it without the dashboard-login challenge, so your
+app's own authentication is the one users and API clients meet. Gitea and
+BTCPay Server ship this way. The node operator can override your default in
+either direction at runtime (Settings → app → Access control), so never
+treat the gate as your app's authorization layer — enforce your own auth on
+every sensitive route regardless. See “Ports & the app gate” in
+[`app-manifest-spec.md`](app-manifest-spec.md).
+
 Set `metadata.launch.open_in_new_tab: true` only when embedding is broken by
 things headers can't fix — the app frame-busts in JavaScript, requires being
 the top-level origin (OAuth redirect flows, WebAuthn), or sets