fix: pass git commit hash as Docker build arg so footer shows correctly

git is not available inside the node:20-alpine Docker image, so
git rev-parse in next.config.ts falls back to 'dev'. Now the commit
hash is passed as a COMMIT_HASH build arg from the host where git
is available, ensuring the footer displays the real commit hash.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.gitea/workflows/deploy.yml

@@ -17,6 +17,7 @@ jobs:
       - name: Build and deploy
         run: |
           cd /home/remmer/StageAI
+          export COMMIT_HASH=$(git rev-parse --short HEAD)
           docker compose build app
           docker compose up -d app
-          echo "Deployed commit: $(git rev-parse --short HEAD)"
+          echo "Deployed commit: $COMMIT_HASH"