feat(syslog): list patterns and add a ready-made one through MCP

Patterns could only be added on the Syslog page, so an agent asked to map
them on the NASes couldn't. list_syslog_patterns gives each pattern's metric
and the ready-made ones not added; add_syslog_preset (admin, audited) adds one.
The key-picking helper moves beside the patterns for both callers.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/core/mcp.md

@@ -85,7 +85,7 @@ Each role includes the tools of the roles above it in this list.
 | Traefik plugin | `list_routers` (each router graded as the Traefik page grades it, with the status codes behind a problem, what they mean and the swarm service behind it), `get_router` (one router's history, codes, normal and anomalies), `list_certificates` (served certificates, days left, the routers they cover), `get_traffic` (the access log's clients, countries and routers, and Traefik's own figures) |
 | UniFi plugin | `get_network` (the WAN, clients, Wi-Fi networks, speed tests and devices by status), `list_devices`, `list_clients` (everyone seen, or the newest poll's top talkers), `list_network_events`, `list_alarms`, `get_network_config` (networks and VLANs, port forwards, firewall rules) |
 | SNMP plugin | `list_snmp_devices` (each device's state, newest readings in their units and the readings it didn't return), `get_snmp_device` (one device's readings over a range). Never the community or v3 keys |
-| Syslog plugin | `list_syslog_sources` (the devices sending syslog: added, offered or ignored, each with its rate, last heard and newest line), `search_syslog` (an added source's kept lines, or a host's, filtered by text, severity and worse, app and time, newest first) |
+| Syslog plugin | `list_syslog_sources` (the devices sending syslog: added, offered or ignored, each with its rate, last heard and newest line), `search_syslog` (an added source's kept lines, or a host's, filtered by text, severity and worse, app and time, newest first), `list_syslog_patterns` (the phrases and severities counted, the metric each writes and the ready-made ones not added), `add_syslog_preset` (admin: add a ready-made one) |
 | Prometheus plugin | `list_prometheus_targets` (each target's state and its newest scrape: series kept, dropped and over the cap), `get_prometheus_target` (a target's stored series by metric, with labels and newest values). Never the token, and a password in a URL is masked |
 
 ### Operator: run playbooks, change monitoring