feat: add GitOps workflow — branch strategy, PR template, deploy/rollback scripts, CI skeleton

- docs/GITOPS.md: complete workflow from prototype to production
- .gitea/pull_request_template.md: pre-merge checklist for swarm PR review
- scripts/deploy.sh: tag-based deployment to all 6 CTs with health checks
- scripts/rollback.sh: rollback to previous tag
- .gitea/workflows/ci.yml: CI pipeline (activates when Actions runners available)
- .gitignore: prevent config.yaml and secrets from being committed
- .gitattributes: consistent LF line endings across platforms

scripts/rollback.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+# rollback.sh — Rollback zulip-platform-plugins to previous tag
+# Usage: ./rollback.sh <previous-tag> [--ct=<agent>]
+set -euo pipefail
+
+TAG="${1:-}"
+SINGLE_CT=""
+
+for arg in "$@"; do
+  case "$arg" in
+    --ct=*) SINGLE_CT="${arg#--ct=}" ;;
+  esac
+done
+
+if [[ -z "$TAG" ]]; then
+  echo "Usage: $0 <previous-tag> [--ct=<agent>]"
+  echo "Example: $0 v0.9.0 --ct=abiba"
+  exit 1
+fi
+
+echo "Rolling back to $TAG..."
+./scripts/deploy.sh --ct="${SINGLE_CT:-all}" "$TAG"