chore(deps): Update actions/checkout action to v7

This PR implements cross-node event broadcasting for aether.

Changes:
- UpdateVersionCache method in JetStreamEventStore
- SubscribeToEventStored helper in NATSEventBus
- Integration tests for cross-node scenarios
- Example code demonstrating NATSEventBus + JetStreamEventStore

Tests: All integration tests passing.
Co-authored-by: Claude Code <noreply@anthropic.com>
Co-authored-by: Hugo Nijhuis <hugo.nijhuis@flowmade.one>
Reviewed-on: #151

.gitea/workflows/ci.yaml

@@ -9,7 +9,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
       - uses: actions/setup-go@v5
         with:
           go-version: '1.23'