Add backup, restore, and Zabbix monitoring docs to Gitea page

Gitea.md

@@ -22,6 +22,51 @@ Repository: https://github.com/alvis/agap_git
 | `/mnt/misc/gitea` | Repositories, config, attachments |
 | `/home/git/.ssh` | SSH keys |
 
+## Backup
+
+Daily backup via cron at 3 AM:
+
+```
+0 3 * * * /home/alvis/agap_git/gitea/backup.sh >> /mnt/backups/gitea/cron.log 2>&1
+```
+
+Script: `gitea/backup.sh` — stops services, runs `gitea dump`, saves zip to `/mnt/backups/gitea/`.
+
+Output: `gitea-dump-*.zip` containing `repos/`, `gitea-db.sql`, `app.ini`, `data/`.
+
+## Restore
+
+Script: `gitea/restore.sh <path-to-dump.zip>`
+
+Stops services, restores DB and data files from the dump zip, starts everything back up, regenerates git hooks.
+
+## Zabbix Monitoring
+
+Config: `/etc/zabbix/zabbix_agent2.d/gitea_backup.conf`
+
+| Key | Returns |
+|-----|---------|
+| `gitea.backup.status` | `1` if last backup succeeded, `0` otherwise |
+| `gitea.backup.age` | Age of latest dump zip in seconds (`-1` if none) |
+
+### Creating Zabbix Trigger Alerts
+
+1. **Create items** — go to *Data collection → Hosts → agap → Items → Create item*:
+   - Name: `Gitea backup status`, Key: `gitea.backup.status`, Type: Zabbix agent (active), Type of information: Numeric (unsigned), Update interval: `1h`
+   - Name: `Gitea backup age`, Key: `gitea.backup.age`, Type: Zabbix agent (active), Type of information: Numeric (unsigned), Update interval: `1h`
+
+2. **Create triggers** — go to *Data collection → Hosts → agap → Triggers → Create trigger*:
+   - **Backup failed:**
+     - Name: `Gitea backup failed`
+     - Severity: High
+     - Expression: `last(/agap/gitea.backup.status)=0`
+   - **Backup stale (>25h):**
+     - Name: `Gitea backup is stale`
+     - Severity: Warning
+     - Expression: `last(/agap/gitea.backup.age)>90000 or last(/agap/gitea.backup.age)=-1`
+
+3. **Verify** — go to *Monitoring → Latest data*, filter by host `agap` and key `gitea.backup`, confirm both items return values.
+
 ## Stack
 
 - Gitea 1.25.3