feat(cloud): retire the Frankfurt relay from Core

[frahlg]

Remote apps now reach Core only through FTW Cloud. Core stops opening the Frankfurt relay socket and stops advertising the old command exchange. Existing inner Noise sessions and Core's command checks stay on the Cloud tunnel. Older app pairings may need a new QR.

Browser box.unreachable notices move to optional, bounded rows in the box-signed service-only roster. Core encrypts the notice and signs the short-lived VAPID authorization at home. The roster binds each subscription to the current enrolled device and epoch; revoked devices vanish before the subscription sweep. The Cloud service uses its existing offline timer and update grace. No HTTP deadman route, second socket or legacy bridge is added.

Anonymous daily reports use https://cloud.ftw.energy/v1/fleet. The exact seven-field report and bounded daily totals live in the public protocol module. An explicitly saved old default resolves to Cloud; private collectors keep their chosen address.

Paired service: srcfl/ftw-cloud#28. Merge this protocol source first, deploy the paired service next, then publish this Core beta. Do not publish the new Core build before the service can accept browser notice rows and fleet reports. Native iOS retirement is srcfl/ftw-app#83; the web client already shipped in srcfl/ftw-webapp#95. Cloud #14 and Core #1633 describe the paused relay-port proposal; this change uses the existing /v1/box and /v1/app tunnel.

Validation: affected Core packages passed with the race detector; fleet schema/bounds, signed Cloud roster and QUIC golden vectors, real box command through Cloud with a trap on the retired relay address, current device epoch and revoke tests. Full local make verify passed (tests, vet, build and protocol/import boundaries). All required CI must pass before merge. No hardware or field soak is claimed. The minor changeset requires a beta; this does not promote stable.

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-17T07:05:36.191605Z	cbdd8a5	PR opened

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