ops: host systemd units in git; windy-pro tags never reach Windy Git

- deploy/systemd/: sync/backup timers+services, tunnel, and the windy-job
  heartbeat drop-ins (silent-failure audit). They existed only on Veron,
  the same drift that left the runbook wrong. GITHUB_TOKEN is stripped
  (repo is public); it stays in the root-only unit on the host.
- sync: SYNC_NO_TAGS (default windy-pro). build-electron fires on v* tags
  and targets ubuntu/macos/windows-latest, labels no runner has, so it
  would queue forever, invisibly. Desktop releases are built elsewhere.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

deploy/systemd/windygit-sync.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=Sync GitHub -> Windy Git (Phase 1: GitHub is the source of truth)
+After=network-online.target docker.service
+
+[Service]
+Type=oneshot
+WorkingDirectory=/srv/windygit/src
+EnvironmentFile=/srv/windygit/src/.env
+# GITHUB_TOKEN is set on the host only (root-only unit file / .env) — NEVER commit it.
+Environment=GITHUB_OWNER=sneakyfree
+ExecStart=/bin/bash /srv/windygit/src/scripts/sync_from_github.sh
+Nice=10