deploy: add auto-deploy script for cron-based podman deploys

Polls origin/main for new commits, builds new image, and swaps
container only if build succeeds. Old container stays running on
build failure.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: brian033

scripts/auto-deploy.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+# Auto-deploy: pull from origin, rebuild if changed, swap container.
+# Usage:
+#   ./scripts/auto-deploy.sh              # 手動跑
+#   */5 * * * * /path/to/auto-deploy.sh   # cron 自動跑
+
+set -euo pipefail
+
+REPO_DIR="$(cd "$(dirname "$0")/.." && pwd)"
+cd "$REPO_DIR"
+
+log() { echo "[$(date '+%Y-%m-%d %H:%M:%S')] $*"; }
+
+log "Checking for updates..."
+git fetch origin main
+
+LOCAL=$(git rev-parse HEAD)
+REMOTE=$(git rev-parse origin/main)
+
+log "Local:  $LOCAL"
+log "Remote: $REMOTE"
+
+if [ "$LOCAL" = "$REMOTE" ]; then
+    log "Already up to date. Nothing to do."
+    exit 0
+fi
+
+log "New commits detected. Pulling..."
+git pull origin main
+log "Pull complete. HEAD is now $(git rev-parse --short HEAD)"
+
+log "Building new image..."
+if podman-compose build; then
+    log "Build succeeded. Stopping old container..."
+    podman-compose down
+    log "Starting new container..."
+    podman-compose up -d
+    log "Deploy complete!"
+else
+    log "BUILD FAILED — old container is still running."
+    exit 1
+fi