Pin the CI toolchain to the SDK this repo actually builds with

`.fvmrc` says 3.47.2 and nothing read it: `subosito/flutter-action` takes its
own `flutter-version:`, and the fleet had drifted to 3.44.6, 3.44.8, 3.44.9,
3.47.0 and 3.47.1 with no one tracking it. kuhylog is the proof it matters --
its runner on 3.44.9 predates the `@awaitNotRequired` annotation, so the same
`unawaited(Navigator.push(...))` is a violation on one SDK and required on the
other, and CI went red on a commit that is clean locally.

The freshness gate reads these pins now (utils@98213cb), so this cannot drift
again in silence.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CRykabMwPgDzFHcARoqpaK

.github/workflows/release-apk.yml

@@ -50,7 +50,7 @@ jobs:
 
       - uses: subosito/flutter-action@v2
         with:
-          flutter-version: 3.44.8
+          flutter-version: 3.47.2
           channel: stable
           cache: true