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>

plugins/syslog/routes.py

@@ -21,7 +21,7 @@ from steward.models.users import UserRole
 from .models import SyslogLine, SyslogPattern, SyslogSource
 from .network import on_own_network
 from .parse import SEVERITIES, facility_name, severity_name
-from .patterns import (PRESETS, PRESETS_BY_KEY, SOURCE_MODULE, WINDOWS, PatternError, key_for, parse_form,
+from .patterns import (PRESETS, PRESETS_BY_KEY, SOURCE_MODULE, WINDOWS, PatternError, free_key, key_for, parse_form,
                        resource_of)
 from .receiver import LISTENER, MAX_SENDERS, send_to, settings
 from .service import (AROUND_LINES, AROUND_SEVERITY, MARK_SEVERITY, MAX_MARKS, PANEL_LINES, PANEL_SPAN,
@@ -339,15 +339,6 @@ async def patterns_index():
                                  any_sources=any(s.state == "accepted" for s in sources.values()))
 
 
-async def _free_key(db, wanted: str) -> str:
-    taken = set((await db.execute(select(SyslogPattern.key))).scalars())
-    key, n = wanted, 2
-    while key in taken:
-        key = f"{wanted[:44]}_{n}"
-        n += 1
-    return key
-
-
 async def _accepted_sources(db) -> list:
     return list((await db.execute(select(SyslogSource).where(SyslogSource.state == "accepted")
                                   .order_by(SyslogSource.name))).scalars())
@@ -368,7 +359,7 @@ async def add_preset(key: str):
         abort(404)
     async with current_app.db_sessionmaker() as db:
         async with db.begin():
-            pattern = SyslogPattern(key=await _free_key(db, preset.key), name=preset.name,
+            pattern = SyslogPattern(key=await free_key(db, preset.key), name=preset.name,
                                     phrases=list(preset.phrases), max_severity=preset.max_severity)
             db.add(pattern)
             await db.flush()
@@ -402,7 +393,7 @@ async def create_pattern():
         async with db.begin():
             if values["source_id"] and await db.get(SyslogSource, values["source_id"]) is None:
                 values["source_id"] = None
-            pattern = SyslogPattern(key=await _free_key(db, key_for(values["name"])), **values)
+            pattern = SyslogPattern(key=await free_key(db, key_for(values["name"])), **values)
             db.add(pattern)
             await db.flush()
             pattern_id = pattern.id