phase 4: drop stale gRPC nomenclature from integration tests

Phase 4 replaced the gateway's authenticated edge listener with a
Connect-Go HTTP/h2c bootstrap that natively serves Connect, gRPC,
and gRPC-Web. Sweep the integration suite so test names, comments,
and helper docs match the new transport posture: rename
TestUserAccount_GetThroughGatewayGRPC to TestUserAccount_GetThroughGatewayEdge,
flip "authenticated gRPC" / "signed gRPC" / "gateway gRPC" comments
to "authenticated edge", and align testenv doc strings.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

integration/testenv/platform.go

@@ -10,7 +10,7 @@ import (
 
 // Platform aggregates a fully booted Galaxy stack: shared Docker
 // network, Postgres, Redis, mailpit, backend and gateway. Tests use
-// this struct to access HTTP/gRPC endpoints, mailpit and backend
+// this struct to access HTTP and authenticated-edge endpoints, mailpit and backend
 // admin without touching testcontainers directly.
 type Platform struct {
 	Network  string