feat(updates): check Gitea automatically and deploy on owner confirmation

Add owner-only update controls, a read-only SSH checker and independent systemd deployment services. Build before maintenance; back up code and database; restore on failed deployment. Preserve runtime configuration and gate business writes during the switch.

deploy/server/config.example.json

@@ -0,0 +1,15 @@
+{
+  "project_dir": "/srv/replypier",
+  "state_dir": "/var/lib/replypier-updater",
+  "repository": "ssh://git@149.71.241.228:10513/WangShen007/replypier.git",
+  "web_url": "http://149.71.241.228:10489/WangShen007/replypier",
+  "branch": "main",
+  "public_url": "https://app.replypier.site",
+  "ssh_key": "/etc/replypier-updater/id_ed25519",
+  "known_hosts": "/etc/replypier-updater/known_hosts",
+  "owner_ids": ["REPLACE_WITH_DEPLOYMENT_OWNER_USER_ID"],
+  "initial_revision": "REPLACE_WITH_INSTALLED_COMMIT",
+  "db_container": "chattermate-local-db-1",
+  "db_user": "chattermate",
+  "db_name": "chattermate"
+}