gatus: show resolved values on successful conditions, ui as a pass-through

Asked to un-hide endpoint properties; the answer is that nothing was hidden.
All six hide-* options (hide-hostname, hide-url, hide-port, hide-conditions,
hide-errors, and dont-resolve-failed-conditions) already default to false
upstream, so hostname, URL, port, conditions and errors were all being shown.

The one setting that genuinely displays MORE is resolve-successful-conditions.
By default a FAILING check resolves its placeholders - "[STATUS] (502) == 200" -
while a PASSING one drops the value and shows only "[STATUS] == 200". With it
on, a healthy DNS check now reads:

    [DNS_RCODE] (NOERROR) == NOERROR
    [BODY] (64.226.70.190) == 64.226.70.190

which says what it actually resolved to rather than merely that the assertion
held. Applied to all 27 pulled endpoints via a gatus_endpoint_default_ui that
each caller can override.

It applies to pulled endpoints ONLY: an external (push) endpoint has no `ui`
field upstream at all, because it carries no conditions - success comes from the
push. The template was initially emitting the block in both loops; emitting an
unknown key into the external-endpoints list risks a parse rejection, and a
rejected config is exactly what skip-invalid-config-update exists to survive.

Also made the page-level `ui` a pass-through dict, the same shape as
gatus_alerting, so every upstream option (description, dashboard-heading, logo,
link, favicon, buttons, custom-css, dark-mode, default-sort-by,
default-filter-by) is reachable without a variable per key. Replaces the two
one-off gatus_ui_title / gatus_ui_header variables.

Set default-sort-by: group, because the dashboard's own grouping toggle starts
OFF and remembers per browser in localStorage - without it the ten groups render
as one flat list of 86 rows for anyone who has not clicked it.

Note the limit of all this: it is configuration. Layout, card design and group
rendering come from the Vue app compiled into the binary (//go:embed static), so
changing those means forking and rebuilding the image - which would discard the
pinned-digest property the deployment relies on.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ansible/roles/gatus/templates/config.yaml.j2

@@ -40,8 +40,7 @@ storage:
   maximum-number-of-events: {{ gatus_storage_max_events }}
 
 ui:
-  title: {{ gatus_ui_title }}
-  header: {{ gatus_ui_header }}
+{{ gatus_ui | to_nice_yaml(indent=2) | indent(2, true) }}
 {% if gatus_alerting %}
 
 alerting: