Phase 7: Cosmos deployment

- Dockerfile with a check target (typecheck and tests) and one image per
  service on a pinned Node 22.20 Alpine base, each with only its own
  production dependencies and a health check.
- deploy/compose.yaml: gk-content, gk-admin and gk-site on homelab_network
  with no host ports, read-only root filesystems, no capabilities, the vault's
  Site folder mounted into the content service, and backup.dump=sqlite on it.
- deploy/deploy.sh builds and checks the commit, restarts the stack, and goes
  back to the last good tag if it doesn't come up healthy; rollback.sh swaps
  tags. .gitea/workflows/deploy.yml runs it on a host runner on Cosmos.
- docs/deploy.md runbook (settings, runner, mirror, NPM hosts, Turnstile,
  Healthchecks, backups, cutover) and the stack's inventory note in vault-kit.
- Site: trusts X-Forwarded-Host/Proto for gregkilmer.com hosts so form posts
  pass Astro's origin check behind the proxy; rate limits read
  CF-Connecting-IP; site URL set for absolute links.
- Content service: the held-change webhook carries a Discord-ready message;
  .env.example lists the core settings.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012aSbo2D1qP8cMFQCykf7kx

deploy/stack.env.example

@@ -0,0 +1,9 @@
+# Stack settings for compose.yaml. On Cosmos: /home/greg/homelab/gregkilmer/.env
+# The Gitea Actions deploy rewrites GK_TAG on every build; GK_PREVIOUS_TAG is the rollback.
+GK_TAG=
+GK_PREVIOUS_TAG=
+# The vault's Site folder on the host.
+VAULT_SITE=/home/greg/homelab/obsidian-vault/20-29_Makerspace/24_Homelab_Infrastructure/24.01_PersonalWebsite/Site
+# The user the containers run as: the owner of the vault files (id -u greg, id -g greg).
+PUID=1000
+PGID=1000