fix(deploy): restore previous release on failure

deploy/deploy.sh

@@ -65,6 +65,8 @@ export APP_VERSION="${APP_VERSION:-0.0.0}"
 export APP_COMMIT_SHA="${APP_COMMIT_SHA:-unknown}"
 export APP_BUILD_STAMP="${APP_BUILD_STAMP:-unknown}"
 export DEPLOY_BUILD_AI_SERVICE="${DEPLOY_BUILD_AI_SERVICE:-false}"
+export BACKEND_IMAGE="${BACKEND_IMAGE:-jobtracker-backend:${APP_COMMIT_SHA}}"
+export FRONTEND_IMAGE="${FRONTEND_IMAGE:-jobtracker-frontend:${APP_COMMIT_SHA}}"
 
 compose() {
   docker compose -f docker-compose.yml "$@"
@@ -477,6 +479,50 @@ if ! backup_database; then
   exit 1
 fi
 
+previous_backend_ref=""
+previous_frontend_ref=""
+capture_previous_core_image() {
+  local service="$1" previous_ref="$2" container_id image_id
+  container_id="$(compose ps -q "$service" 2>/dev/null || true)"
+  [ -n "$container_id" ] || return 0
+  image_id="$(docker inspect -f '{{.Image}}' "$container_id" 2>/dev/null || true)"
+  [ -n "$image_id" ] || return 0
+  docker tag "$image_id" "$previous_ref"
+  printf '%s' "$previous_ref"
+}
+
+previous_backend_ref="$(capture_previous_core_image backend jobtracker-backend:previous)"
+previous_frontend_ref="$(capture_previous_core_image frontend jobtracker-frontend:previous)"
+replacement_started=false
+auth_config_body_file=""
+auth_config_headers_file=""
+
+finish_deploy() {
+  local status=$?
+  trap - EXIT
+  [ -z "$auth_config_body_file" ] || rm -f "$auth_config_body_file"
+  [ -z "$auth_config_headers_file" ] || rm -f "$auth_config_headers_file"
+
+  if [ "$status" -ne 0 ] && [ "$replacement_started" = true ]; then
+    if [ -n "$previous_backend_ref" ] && [ -n "$previous_frontend_ref" ]; then
+      echo "Deployment failed after core replacement; restoring previous healthy images."
+      if BACKEND_IMAGE="$previous_backend_ref" FRONTEND_IMAGE="$previous_frontend_ref" \
+          compose up -d --force-recreate --remove-orphans backend frontend; then
+        echo "Previous core release restored. Deployment remains failed; inspect the logs above."
+      else
+        echo "Automatic core rollback failed. Manual recovery is required."
+        compose ps || true
+        compose logs --tail=200 backend frontend || true
+      fi
+    else
+      echo "Deployment failed, but no complete previous core release was available for automatic rollback."
+    fi
+  fi
+
+  exit "$status"
+}
+trap finish_deploy EXIT
+
 build_core_with_recovery() {
   if compose build backend frontend; then
     return 0
@@ -500,7 +546,6 @@ build_ai_with_recovery() {
   compose build --no-cache ai-service
 }
 
-compose pull || true
 build_core_with_recovery
 if [ "$DEPLOY_BUILD_AI_SERVICE" = "true" ]; then
   build_ai_with_recovery
@@ -508,6 +553,7 @@ else
   echo "Skipping ai-service rebuild during deploy (set DEPLOY_BUILD_AI_SERVICE=true to rebuild it)."
 fi
 # Force recreation so updated port mappings, env vars, and container config always apply on deploy.
+replacement_started=true
 compose up -d --force-recreate --remove-orphans backend frontend
 if [ "$DEPLOY_BUILD_AI_SERVICE" = "true" ]; then
   # Ollama is opt-in (compose "bundled-ollama" profile). Deploys reuse an
@@ -539,10 +585,6 @@ fi
 public_base="${APP_PUBLIC_BASE_URL%/}"
 auth_config_body_file="$(mktemp)"
 auth_config_headers_file="$(mktemp)"
-cleanup_public_check() {
-  rm -f "$auth_config_body_file" "$auth_config_headers_file"
-}
-trap cleanup_public_check EXIT
 
 echo "Running public smoke check against ${public_base}"
 if ! curl -fsS "${public_base}/" >/dev/null; then
@@ -579,10 +621,8 @@ if ! grep -q 'requireAuth' "$auth_config_body_file"; then
   exit 1
 fi
 
-trap - EXIT
-cleanup_public_check
-
 # Clean up old legacy container name if it still exists from pre-rename deployments.
 docker rm -f app-summarizer-1 2>/dev/null || true
 
+replacement_started=false
 echo "Deployment complete: ${APP_VERSION} ${APP_COMMIT_SHA}"