Fix deploy: filter out non-app packages from build matrix

Turbo's change detection includes shared packages like @homelab/db,
which don't have Dockerfiles. Filter to only apps with a Dockerfile
to prevent 'path not found' errors during docker build.

.gitea/workflows/deploy-production.yaml

@@ -36,7 +36,7 @@ jobs:
               APPS="$INPUT"
             fi
           else
-            APPS=$(pnpm turbo build --filter='...[HEAD~1]' --dry-run=json | jq -r '[.packages[] | select(startswith("@homelab/")) | sub("@homelab/";"") ] | join(",")')
+            APPS=$(pnpm turbo build --filter='...[HEAD~1]' --dry-run=json | jq -r '[.packages[] | select(startswith("@homelab/")) | sub("@homelab/";"") ] | join(",")' | tr ',' '\n' | while read app; do [ -f "apps/${app}/Dockerfile" ] && echo "$app"; done | paste -sd, -)
           fi
           echo "apps=$APPS" >> "$GITHUB_OUTPUT"