feat(relay): declare Asia spare cell c34 as migration-only (#25336)

Adds a sixth asia-east2 cell at the C31 shape (cap 3000, 6000 request
units, pool 16, e2-standard-4) in asia-east2-c, pinned to the f30b5cb1
cell image. It gets its own topology and registration wave but no
promotion wave, so the admission script and workflow refuse to promote
it; it stays a migration-only landing zone and out of the fleet pool list.

Claude-Session: 1145a80d-dec4-4a9b-9373-bbbb876b9041

.github/workflows/cloud-deploy-relay-asia-topology.yml

@@ -78,6 +78,7 @@ jobs:
             production:production-gce-c30) ;;
             production:production-gce-c31) ;;
             production:production-gce-c32,production-gce-c33) target_region=us-central1 ;;
+            production:production-gce-c34) ;;
             *) echo "cell-ids do not match the reviewed environment topology" >&2; exit 1 ;;
           esac
           echo "TARGET_REGION=${target_region}" >> "${GITHUB_ENV}"

.github/workflows/cloud-deploy-relay-production-same-cap-job.yml

@@ -194,7 +194,7 @@ jobs:
               EXPECTED_REGION=us-central1
               EXPECTED_DATABASE_POOL_MAX=
               ;;
-            c27|c28|c29|c30|c31)
+            c27|c28|c29|c30|c31|c34)
               EXPECTED_HARD_CAP=3000
               EXPECTED_REGION=asia-east2
               EXPECTED_DATABASE_POOL_MAX=16