Initial taiko.su easter-egg site

MONGODB_SAFETY.md

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+# MongoDB Safety Notes
+
+Default paths:
+
+- App directory: `/srv/taiko-web`
+- Persistent data directory: `/srv/taiko-web-data`
+- MongoDB data directory: `/srv/taiko-web-data/mongo`
+- Redis data directory: `/srv/taiko-web-data/redis`
+- Song file directory: `/srv/taiko-web-data/songs`
+- MongoDB backup directory: `/srv/taiko-web/backups/mongodb/YYYYMMDD-HHMMSS/`
+
+Safe commands:
+
+```bash
+sudo bash setup.sh install
+sudo bash setup.sh update
+sudo bash setup.sh backup-db
+sudo bash setup.sh restore-db /srv/taiko-web/backups/mongodb/YYYYMMDD-HHMMSS/mongodump
+sudo bash setup.sh repair
+```
+
+`setup.sh update` does not delete MongoDB data. When existing data is detected, it pauses application writers (`taiko-web-app` and/or the `taiko-web` systemd service), keeps MongoDB online, creates a `mongodump` backup, then updates and starts the new app service. If the backup or update fails before the app is replaced, the script attempts to restart the previously running app service.
+
+`setup.sh backup-db` uses the same consistency-first behavior: pause app writes, run `mongodump`, then resume the app service that was running before the backup.
+
+`setup.sh` keeps an existing `.env` file and only appends missing keys. It also excludes `.env` and `backups` from source sync deletion.
+
+Dangerous database reset is explicit only:
+
+```bash
+sudo bash setup.sh reset-db
+```
+
+The reset command requires typing:
+
+```text
+I_UNDERSTAND_THIS_WILL_DELETE_MONGODB_DATA
+```
+
+Normal install and update flows must not run `docker compose down -v`, remove Docker volumes, or remove `/srv/taiko-web-data/mongo`.