feat(monitors): problems first, a page per monitor, adding on its own page (#5121)

The Monitors list now opens with a count strip (down, up with how many
degraded, pending, paused) and sorts down, degraded, pending, up, paused,
by name within each. Degraded is up but worth a look: uptime at or below
its warning floor, or the latest response past its critical cutoff, both
from Settings → Thresholds; a slow-but-tolerable reply is coloured, not
sorted.

A monitor had no page of its own: every link went to the list. Now
/monitors/<id> shows its state and since when, latency, uptime for 24h/7d/
30d, TLS days, the last checks, recent failures with their errors, and its
settings (HTTP header names, never their values). Status links to it, and
adding or editing returns to it.

Adding is its own page (/monitors/new, form.html shared with edit) behind
an "Add monitor" button; a refused add re-renders the form with the error
and what was typed instead of a bare 400 text. Row actions are labelled
icon buttons, type names read Ping/TCP/DNS/HTTP (|monitor_type), and the
heartbeat uses pill-up/pill-down, so HEX_CEILING drops to 56.

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

steward/models/monitors.py

@@ -23,6 +23,8 @@ class MonitorType(str, enum.Enum):
 # DROP/ADD CONSTRAINT (family rule 36) instead of the heavier ALTER TYPE ADD
 # VALUE a native enum would force.
 MONITOR_TYPE_VALUES = tuple(t.value for t in MonitorType)
+# How a page names each type.
+MONITOR_TYPE_LABELS = {"icmp": "Ping", "tcp": "TCP", "dns": "DNS", "http": "HTTP"}
 _TYPE_CHECK = "type IN ('icmp', 'tcp', 'dns', 'http')"