refactor(push): one app profile per gateway (#8206)

Buzz push currently selects an application profile, such as `dogfood`,
during client registration. We want each gateway to serve one Apple app
configured by the operator instead. This removes profile selection from
the client, relay, and gateway, while allowing internal and public
gateways to use their own Apple identities.

This PR implements that model in the Buzz source and upstream deployment
chart. Discovery, enrollment, grants, and leases no longer carry an
application-profile selector. Each gateway has one configured Apple
application and APNs transport.

The protocol changes are incompatible with the old registration format,
so relays advertise `buzz-push-v1` instead of `nip-pl`. Old clients do
not discover the new push capability. Updated clients use separate
Keychain records and register again. The [push
notes](https://github.com/block/buzz/blob/push-capability-v1/docs/buzz-push.md)
describe the experimental contract.

Landing this PR is the first step. Publish the matching gateway image
and upstream chart, then land the [shared chart
update](https://github.com/squareup/cash-helm-charts/pull/5740) and
[gateway deployment
update](https://github.com/squareup/builderbot-platform-core-infrastructure/pull/1085).
Before cutover, stop old gateway instances and check legacy registration
state. Migrations refuse to proceed if old gateway installations or
active relay leases remain; they do not delete that state.
Physical-device verification remains necessary before production
activation.

### Validation
Gateway and focused Flutter push tests pass, as do the Swift package,
simulator build, and native notification/enrichment tests. A local relay
advertises `buzz-push-v1` without `nip-pl` or `app_profiles`. The
PostgreSQL suite passed 868 tests; its two migration-test failures were
corrected and pass a focused rerun together with the gateway cutover
guard. Chart rendering and release-contract checks pass.

Desktop JavaScript tests, desktop and web builds, native desktop
compilation, mobile analysis/tests, and desktop native tests pass. The
full Rust unit lane and prescribed `just test` command pass, including
workspace integration tests against task-isolated local services. The
production overlay now requires an explicitly supplied APNs topic, with
omission and rendered-value regression coverage. The corrected Swift
checksum assertion passes the complete package suite: 78 XCTest tests
and 42 Swift Testing tests. No physical-device enrollment or production
cutover is claimed.

Local merge validation: the embedded migration test and formatting pass
after reserving profile migration 0060 behind rollback migration 0059.
The local pre-push Rust lane failed ACP timing/steering tests
(`idle_resets_on_stdout_activity`,
`keepalive_resets_idle_past_deadline`, and the failed/missing-outcome
steering tests). ACP and its dependency manifests are unchanged by this
branch; all four pass in an isolated single-thread rerun. The documented
local-check exception skips only the Rust pre-push lane for publication;
required CI remains mandatory. Mobile and desktop pre-push lanes passed.

Combined migration validation: after rollback 0059 landed, the main
merge preserves profile migration 0060 and both embedded migration
assertions. The focused migration test and formatting pass. The next
local push again failed only the unchanged ACP idle/keepalive timing
tests (1053 passed, 2 failed, 3 ignored); other lanes passed.
Publication uses the same documented local Rust-lane exception; required
CI remains mandatory.

Follow-up review fix: removed the legacy profile column from the
copied-lease fixture. All four event-follow-up contract tests pass on
isolated PostgreSQL databases, covering desired and migrated schemas in
dual and app-only modes. Formatting passes. Publication retains the
prior passing local-lane evidence and uses the authorized pre-push
exception for the known unrelated ACP timing failures; required CI
remains mandatory.

---------

Signed-off-by: Tom Brow <tomb@block.xyz>

docs/buzz-push.md

@@ -0,0 +1,21 @@
+# Buzz push notes
+
+Push is experimental. These notes capture current decisions; we will write a
+stable specification after validating the design through launch and use.
+[NIP-PL](nips/NIP-PL.md) is background, not the current Buzz contract.
+
+- Relays advertise `buzz-push-v1`, never `nip-pl`. Updated clients require it.
+- Compatible changes keep the capability name. Incompatible behavior that
+  clients must distinguish gets a new version.
+- Each gateway serves one server-configured Apple application and APNs transport.
+  Enrollment, transcripts, grants, leases and discovery have no application-profile
+  selector. The relay advertises transport classes in `class_support`.
+- Existing grants and pending enrollment records are not migrated. The new client
+  uses separate Keychain records and enrolls again. Keep old production push
+  disabled so released clients never acquire legacy push authority.
+- Stop old gateway replicas before cutover. The gateway migration requires an
+  empty authority store because endpoint fingerprints changed. The relay migration
+  requires no active legacy leases. Neither migration deletes that state.
+- Publish the matching gateway image and chart, update deployment configuration,
+  then enable the new relay capability. Verify enrollment, delivery, renewal and
+  revocation on a physical device before production activation.