feat(120): alert component unification

Phase 120 - Plan 01:
- Reusable PHP alert component (resources/views/components/alert.php)
  with inline SVG icon per type, optional dismiss button.
- Missing .alert--info SCSS variant added (#eff6ff/#bfdbfe/#1e3a8a) -
  fixes black-on-white alert after Fakturownia test connection.
- Flash::push(type, message) + Flash::all() with BC for set/get;
  legacy key heuristic (error/.save/warning -> typed entries).
- Central flash renderer in 3 layouts (app/auth/public) iterating
  Flash::all() through component (.alerts-stack wrap).
- Vanilla JS alert-dismiss.js with idempotent guard and delegated
  click handler on [data-alert-dismiss].
- 36 views migrated off inline <div class="alert alert--TYPE">;
  .flash--error/success removed from views (orders/show, shipments/prepare).
- SCSS rebuilt: public/assets/css/{app,login}.css.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

resources/views/layouts/app.php

@@ -184,6 +184,17 @@
       </header>
 
       <main class="container">
+        <?php $flashEntries = \App\Core\Support\Flash::all(); ?>
+        <?php if (!empty($flashEntries)): ?>
+          <div class="alerts-stack" data-flash-stack>
+            <?php foreach ($flashEntries as $flashEntry): ?>
+              <?php $type = (string) ($flashEntry['type'] ?? 'info'); ?>
+              <?php $message = (string) ($flashEntry['message'] ?? ''); ?>
+              <?php $dismissible = true; ?>
+              <?php include __DIR__ . '/../components/alert.php'; ?>
+            <?php endforeach; ?>
+          </div>
+        <?php endif; ?>
         <?= $content ?>
       </main>
     </div>
@@ -194,6 +205,7 @@
   <script src="/assets/js/modules/invoice-config-form.js?ver=<?= filemtime(dirname(__DIR__, 3) . '/public/assets/js/modules/invoice-config-form.js') ?: 0 ?>"></script>
   <script src="/assets/js/modules/invoice-requested-toggle.js?ver=<?= filemtime(dirname(__DIR__, 3) . '/public/assets/js/modules/invoice-requested-toggle.js') ?: 0 ?>"></script>
   <script src="/assets/js/modules/confirm-delete.js?ver=<?= filemtime(dirname(__DIR__, 3) . '/public/assets/js/modules/confirm-delete.js') ?: 0 ?>"></script>
+  <script src="/assets/js/modules/alert-dismiss.js?ver=<?= filemtime(dirname(__DIR__, 3) . '/public/assets/js/modules/alert-dismiss.js') ?: 0 ?>"></script>
   <script src="https://cdn.jsdelivr.net/npm/chart.js@4.4.8/dist/chart.umd.min.js"></script>
   <script src="/assets/js/modules/statistics-summary-charts.js?ver=<?= filemtime(dirname(__DIR__, 3) . '/public/assets/js/modules/statistics-summary-charts.js') ?: 0 ?>"></script>
   <script>