Add admin password reset script and docs

Co-Authored-By: Oz <oz-agent@warp.dev>

README.md

@@ -64,6 +64,21 @@ This script will:
 ```bash
 ./scripts/renew-production-tls.sh
 ```
+## Admin password reset
+List existing users:
+```bash
+docker exec --user www-data nextcloud-app php occ user:list
+```
+Reset password using helper script (interactive prompt):
+```bash
+./scripts/reset-admin-password.sh admin
+```
+Reset password non-interactively (for automation):
+```bash
+NEW_NEXTCLOUD_PASSWORD={{NEW_NEXTCLOUD_PASSWORD}} ./scripts/reset-admin-password.sh admin
+```
+You can target a different username by passing it as the first argument.
+
 ## Useful commands
 Start/update containers:
 ```bash