ci: opt JS actions into Node.js 24

GitHub deprecated Node.js 20 for actions; runners will force Node 24 by
June 2 2026. Opting in now via the documented FORCE_JAVASCRIPT_ACTIONS_TO_NODE24
env var instead of pinning every action version. Applied to both
firmware-build (PR check) and release (tag-driven) workflows.

.github/workflows/firmware-build.yml

@@ -11,6 +11,9 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: ${{ github.event_name == 'pull_request' }}
 
+env:
+  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
+
 jobs:
   representative-build:
     name: Representative build (Heltec V3, RAK 4631)

.github/workflows/release.yml

@@ -18,6 +18,9 @@ concurrency:
   group: release-${{ github.ref }}
   cancel-in-progress: false
 
+env:
+  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
+
 jobs:
   enumerate:
     name: Enumerate companion targets