fix(ci): unify migration-compose issue label with migration-test (#259)

Follow-up to #256. The compose job's issue lifecycle was using a
separate `migration-compose` label, fragmenting the issue list and
the team's triage. Per review feedback after merge, the docker-compose
job is just the migration test running in a different deployment
environment — not a separate concern. Both jobs now share the
`migration-test` label so failures fold into a single issue lifecycle.

The compose failure body still mentions the docker-compose variant in
plain text, so source is distinguishable on read.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: lice-reis

.github/workflows/migration-test.yml

@@ -535,7 +535,7 @@ jobs:
             const { data: existing } = await github.rest.issues.listForRepo({
               owner: context.repo.owner,
               repo: context.repo.repo,
-              labels: 'migration-compose',
+              labels: 'migration-test',
               state: 'open',
             });
             if (existing.length > 0) {
@@ -568,7 +568,7 @@ jobs:
             const { data: existing } = await github.rest.issues.listForRepo({
               owner: context.repo.owner,
               repo: context.repo.repo,
-              labels: 'migration-compose',
+              labels: 'migration-test',
               state: 'open',
             });
             const body = [
@@ -593,8 +593,8 @@ jobs:
               await github.rest.issues.create({
                 owner: context.repo.owner,
                 repo: context.repo.repo,
-                title: 'Langflow Migration via docker-compose Failed (latest → nightly)',
+                title: 'Langflow Migration Test Failed (latest → nightly)',
                 body,
-                labels: ['migration-compose', 'automated'],
+                labels: ['migration-test', 'automated'],
               });
             }