Initial import of Shirobana bot backend

Include utility modules, shared channels, prompts, read-only skills, wardrobe memory and regression tests. Externalize legacy credentials and exclude private runtime state.

bot-utility.service

@@ -0,0 +1,23 @@
+# Deployment template: adjust user, checkout path and EnvironmentFile before use.
+[Unit]
+Description=Shirobana utility bot backend
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=shirobana
+Group=shirobana
+WorkingDirectory=/opt/shirobana-bot/bot-utility
+ExecStart=/opt/shirobana-bot/bot-utility/.venv/bin/python -B /opt/shirobana-bot/bot-utility/main.py
+Environment=PYTHONUNBUFFERED=1
+Environment=TZ=Asia/Shanghai
+EnvironmentFile=/etc/shirobana-bot/bot.env
+Restart=on-failure
+RestartSec=10
+TimeoutStopSec=30
+KillMode=control-group
+UMask=0077
+
+[Install]
+WantedBy=multi-user.target