Consolidate all expose business logic (validation, permission checks, TTL tracking, reaping) into the manager layer, making the gRPC layer a pure transport adapter that only handles proto conversion and authentication.
- Add ExposeServiceRequest/ExposeServiceResponse domain types with validation in the reverseproxy package
- Move expose tracker (TTL tracking, reaping, per-peer limits) from gRPC server into manager/expose_tracker.go
- Internalize tracking in CreateServiceFromPeer, RenewServiceFromPeer, and new StopServiceFromPeer so callers don't manage tracker state
- Untrack ephemeral services in DeleteService/DeleteAllServices to keep tracker in sync when services are deleted via API
- Simplify gRPC expose handlers to parse, auth, convert, delegate
- Remove tracker methods from Manager interface (internal detail)
CLI: new expose command to publish a local port with flags for PIN, password, user groups, custom domain, name prefix and protocol (HTTP default).
Management/API: create/renew/stop expose sessions (streamed status), automatic naming/domain, TTL renewals, background expiration, new management RPCs and client methods.
UI/API: account settings now include peer_expose_enabled and peer_expose_groups; new activity codes for peer expose events.
