docs: add SQL-only schema update script for v2610.1

update(2610.1).sql brings an existing database up to the current schema
without PHP: base tables (CREATE IF NOT EXISTS), the v2603.x migrations
(last_event_at column, uq_event removal) and the v2610.1 index changes
(idx_occurred, idx_src_ip_occ, drop idx_src_ip). All steps are idempotent
via information_schema checks + PREPARE/EXECUTE, so the file is safe to
re-run and portable across MySQL 8 and MariaDB.

README.md

@@ -42,6 +42,7 @@ Each portspoof_py instance runs independently and exposes a JSON API. portspoof_
 portspoof_concentrator/
 ├── config.php            Database credentials and app-wide constants
 ├── schema.sql            MySQL DDL (applied by setup.php)
+├── update(2610.1).sql    SQL-only schema update for existing databases (this release)
 ├── setup.php             One-time install / migration script
 ├── index.php             Aggregated dashboard
 ├── nodes.php             Add / edit / delete portspoof_py nodes
@@ -501,13 +502,21 @@ curl -H "Authorization: Bearer your-token" "https://yourserver/api/connections.p
 
 ## Upgrading
 
-If you deployed before `last_event_at` was added to the schema, run `setup.php` again:
+When upgrading, migrate the database to the new schema with either of:
+
+**Via the PHP setup script:**
 
 ```bash
 php /var/www/portspoof_concentrator/setup.php
 ```
 
-It will add the missing column, drop the legacy `uq_event` unique key, and add the `occurred_at` / `(src_ip, occurred_at)` indexes if present. No data is lost.
+**Via SQL (no PHP required):**
+
+```bash
+mysql -u portspoof -p portspoof_concentrator < "update(2610.1).sql"
+```
+
+Both apply all pending migrations idempotently (the `last_event_at` column, the legacy `uq_event` key removal, and the `occurred_at` / `(src_ip, occurred_at)` indexes) and can be re-run safely. No data is lost. Note that on a large `connections` table the `ADD KEY` steps take time proportional to the table size.
 
 ---