Rebuild the dashboard around what needs a person

The board was one card per source in a fixed grid: every source got the same
small box whatever it had to say (warranties showed 5 of 50), and a box per
source flattened priority, while the largest type on the page belonged to counts
that need nobody.

Now a severity rollup, one worst-first queue of everything needing a person, and
a row of context beneath. The queue is full width, capped per source so a noisy
check cannot bury a rare one, and names what did not fit with a link to it. Chips
filter the queue by check as well as by severity; both narrow what is already
loaded, so the counts and rows cannot disagree.

Dropped: an 'All assets' tile shown beside its own four addends, a printer strip
carrying the same count a third time, three cards whose job was to display 0, and
a Recent Devices table listing five machines all 'In Use'.

Contract 0.26.0 adds optional 'shortname' on dashboard cards - a title is written
as a heading and ran wider than the hostname it qualified as a row badge.

Also: the supplies card reported 'Low Supplies 0' when Zabbix was unreachable,
which reads as reassurance rather than the truth that nothing could see the
cartridges. It now distinguishes unreachable (says so) from unconfigured (stays
quiet - the site declined the feature) from a real zero.

Full suite 2182 passed, frontend 314 passed.

plugins/endpoints/plugin.py

@@ -387,6 +387,7 @@ class EndpointsPlugin(BasePlugin):
                 'id': 'endpoints-quiet',
                 'viewall': '/pcs',
                 'title': 'Endpoints gone quiet',
+                'shortname': 'Agent quiet',
                 'endpoint': '/api/endpoints/dashboard/quiet',
                 'render': 'exceptions',
                 'severity': 'warning',
@@ -405,6 +406,7 @@ class EndpointsPlugin(BasePlugin):
                 'id': 'endpoints-stability',
                 'viewall': '/pcs',
                 'title': 'Endpoints with crashes or shutdowns',
+                'shortname': 'Crashes',
                 'endpoint': '/api/endpoints/dashboard/stability',
                 'render': 'exceptions',
                 'severity': 'critical',