feat(syslog): a source's lines to read and search, on its page, its host's and its SNMP device's, and over MCP (#6000)

- /plugins/syslog/sources/<id>: the lines newest first, loading as you
  scroll, filtered by severity and worse, app, text and time, with day
  dividers and times to the second in the reader's zone.
- The Syslog page links each source and shows its lines in the last hour.
- A Syslog panel on a host's page and an SNMP device's: the newest lines of
  the sources bound to it or at its address.
- MCP: list_syslog_sources and search_syslog (source, host, text, severity
  and worse, app, range, paging by next_before).
- Shared: escape_like moves to steward/core/like.py and cut_middle to the
  MCP shaping module, replacing four inline copies; |when takes seconds=.

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

steward/app.py

@@ -147,7 +147,8 @@ def create_app(
         from quart import has_request_context, session
         return _fmt.zone(session.get("tz")) if has_request_context() else _fmt.zone(None)
     app.jinja_env.filters["ago"] = lambda moment, now=None: _fmt.ago(moment, now, tz=_viewer_zone())
-    app.jinja_env.filters["when"] = lambda moment: _fmt.when(moment, _viewer_zone())
+    app.jinja_env.filters["when"] = lambda moment, seconds=False: _fmt.when(moment, _viewer_zone(),
+                                                                             seconds=seconds)
     app.jinja_env.globals["tz_label"] = lambda: _fmt.tz_label(_viewer_zone())
     app.jinja_env.globals["status_class"] = (
         lambda value, kind: _fmt.status_class(value, kind, app.config.get("THRESHOLDS", {}))