Add README with setup and backup instructions

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

README.md

@@ -1,2 +1,30 @@
-# gitea
+# Gitea
 
+Self-hosted Gitea instance running on Docker Compose with a remote PostgreSQL database and automated daily backups.
+
+## Services
+
+- **gitea** — Web UI on port `3008`, SSH on port `2222`
+- **gitea-backup** — Alpine sidecar running a daily cron job at 2 AM
+
+## Setup
+
+```bash
+docker-compose up -d
+```
+
+## Backups
+
+Backups run automatically at 2 AM daily, writing `gitea-dump-*.zip` files to `/mnt/nasen/backup/gitea` with 7-day retention.
+
+Run a manual backup:
+
+```bash
+docker exec gitea-backup /usr/local/bin/backup.sh
+```
+
+Check backup logs:
+
+```bash
+docker exec gitea-backup cat /var/log/backup.log
+```