Add CI, a pre-commit hook, and an accessibility pass on the panel's own views

CI (.github/workflows/tests.yml) reuses docker-compose.test.yml verbatim for
the Postgres job rather than re-describing that environment in YAML, so the
Docker image stays the single source of truth for it.

Fixes a real mismatch found while wiring PHP versions into the workflow:
composer.json declared "php": "^8.3", but the locked Symfony packages require
>=8.4.1 — installing on 8.3 would fail at `composer install`, exactly what
the Dockerfile's own comment already warned about. Bumped the constraint and
resynced composer.lock's content-hash (no package versions changed).

The pre-commit hook (.githooks/pre-commit, activated via
`git config core.hooksPath` in post-autoload-dump) runs `pint --dirty --test`
and refuses to commit unformatted files rather than silently rewriting them.

The accessibility pass only touches this app's own hand-written Blade views,
not Filament's components: aria-hidden on icons that repeat adjacent text,
an aria-label on the one icon that is the only signal of a health check's
severity, rel="noopener" and a labelled announcement on preview links that
open in a new tab.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

resources/views/filament/pages/site-health.blade.php

@@ -1,11 +1,18 @@
 <x-filament-panels::page>
     {{-- The headline. Whether anything is actually wrong is the one thing
-         somebody opening this page came to find out. --}}
+         somebody opening this page came to find out.
+
+         Most of the icons below are `aria-hidden`: colour and shape repeating
+         what the text beside them already says. The one on each check's own
+         heading is the exception — severity there is never written out in
+         words, only implied by an icon and a badge colour — so that one gets
+         a spoken name instead of being hidden. --}}
     @if ($this->problems()->isEmpty())
         <div class="rounded-xl border border-success-300 bg-success-50 p-4 dark:border-success-700/50 dark:bg-success-500/10">
             <div class="flex items-center gap-3">
                 <x-filament::icon
                     icon="heroicon-o-check-circle"
+                    aria-hidden="true"
                     class="h-5 w-5 shrink-0 text-success-600 dark:text-success-400"
                 />
 
@@ -25,6 +32,7 @@
             <div class="flex items-start gap-3">
                 <x-filament::icon
                     icon="heroicon-o-exclamation-triangle"
+                    aria-hidden="true"
                     @class([
                         'mt-0.5 h-5 w-5 shrink-0',
                         'text-danger-600 dark:text-danger-400' => $tone === 'danger',
@@ -60,6 +68,8 @@
                 <span class="flex items-center gap-2">
                     <x-filament::icon
                         :icon="$finding->severity->getIcon()"
+                        :aria-label="$finding->severity->getLabel()"
+                        role="img"
                         @class([
                             'h-5 w-5 shrink-0',
                             'text-danger-500' => $finding->severity->getColor() === 'danger',
@@ -123,6 +133,7 @@
                     <li class="flex items-start gap-2 text-sm">
                         <x-filament::icon
                             icon="heroicon-o-check-circle"
+                            aria-hidden="true"
                             class="mt-0.5 h-4 w-4 shrink-0 text-success-500"
                         />