refactor(file-upload): SSR-first state, click-to-replace, cleaner preview

- Server renders initial file-upload state (src, alt, label text,
  has-current class) so there is no flash of broken-image icon while
  JS boots. JS no longer duplicates that work — it only reacts to
  user input (select, clear, drag-and-drop) and uses data-current-src
  solely to restore the server file after a blob preview.
- Clicking the current preview image now opens the file dialog, mirrors
  the Replace button, with hover affordance (cursor + primary border).
- Drop the transparency checker pattern in the preview — the admin UI
  does not need Figma-style transparency semantics. Preview is now a
  flat theme-aware surface (--app-preview-bg) that keeps white or
  black logos visible against a neutral gray.
- Move tenant favicon out of the aside into the Master-data tab as its
  own details block next to the Tenant-logos section. Uses the same
  barrier-form pattern (HTML5 form attribute + app-file-upload.phtml)
  for a consistent instant-upload UX.
- Tenant-logo slot label is a native <label> element — picks up the
  global form-label typography and spacing, no custom muted-color
  class needed.

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

pages/admin/tenants/_form.phtml

@@ -235,6 +235,35 @@ $openOverrideCard = $detailsOpenAll;
         </div>
       </details>
       <hr>
+      <details name="tenant-master-favicon" <?php e($detailsOpenAll ? 'open' : ''); ?>>
+        <summary><?php e(t('Tenant favicon')); ?></summary>
+        <hr>
+        <?php
+        $tenantFaviconUuid = (string) ($values['uuid'] ?? '');
+        $faviconPresent = $hasFavicon ?? false;
+        $fileUpload = [
+            'name' => 'favicon',
+            'accept' => 'image/png',
+            'hint' => t('Square PNG. Icons are center-cropped.'),
+            'currentSrc' => $faviconPresent && $tenantFaviconUuid !== ''
+                ? asset('favicon/tenants/' . $tenantFaviconUuid . '/favicon/favicon-32x32.png')
+                : '',
+            'currentLabel' => t('Favicon'),
+            'formId' => 'tenant-favicon-form',
+            'deleteFormId' => $faviconPresent ? 'tenant-favicon-delete-form' : '',
+            'deleteConfirm' => t('Delete this favicon?'),
+        ];
+        require templatePath('partials/app-file-upload.phtml');
+        ?>
+        <?php if ($canUpdateTenant): ?>
+          <div class="tenant-logo-actions">
+            <button type="submit" form="tenant-favicon-form" class="secondary outline small">
+              <?php e(t('Save')); ?>
+            </button>
+          </div>
+        <?php endif; ?>
+      </details>
+      <hr>
       <details name="tenant-master-contact" <?php e($detailsOpenAll ? 'open' : ''); ?>>
         <summary><?php e(t('Contact')); ?></summary>
         <hr>

pages/admin/tenants/edit(default).phtml

@@ -77,6 +77,14 @@ $hasFavicon = $tenantUuid !== '' && $tenantFaviconService->hasFavicon($tenantUui
         <input type="hidden" name="theme" value="dark">
         <?php Session::getCsrfInput(); ?>
       </form>
+      <form id="tenant-favicon-form" method="post"
+        action="admin/tenants/favicon/<?php e($tenantUuid); ?>" enctype="multipart/form-data" hidden>
+        <?php Session::getCsrfInput(); ?>
+      </form>
+      <form id="tenant-favicon-delete-form" method="post"
+        action="admin/tenants/favicon-delete/<?php e($tenantUuid); ?>" hidden>
+        <?php Session::getCsrfInput(); ?>
+      </form>
     <?php endif; ?>
 
     <?php
@@ -112,35 +120,6 @@ $hasFavicon = $tenantUuid !== '' && $tenantFaviconService->hasFavicon($tenantUui
         <p><?php e(t('Tenant')); ?></p>
       </hgroup>
       <hr>
-      <?php if ($canUpdateTenant): ?>
-        <details name="tenant-favicon">
-          <summary>
-            <?php e(t('Upload favicon')); ?>
-          </summary>
-          <hr>
-          <small><?php e(t('Square images are recommended (icons are center-cropped).')); ?></small>
-          <hr>
-          <form class="user-avatar-form" method="post" action="admin/tenants/favicon/<?php e($tenantUuid); ?>"
-            enctype="multipart/form-data">
-            <?php
-            $fileUpload = [
-                'name' => 'favicon',
-                'accept' => 'image/png',
-                'hint' => t('Allowed file types: PNG'),
-                'currentSrc' => $hasFavicon ? asset('favicon/tenants/' . $tenantUuid . '/favicon/favicon-32x32.png') : '',
-                'currentLabel' => t('Favicon'),
-                'deleteAction' => $hasFavicon ? 'admin/tenants/favicon-delete/' . $tenantUuid : '',
-            ];
-            require templatePath('partials/app-file-upload.phtml');
-            ?>
-            <button type="submit" class="app-action-success">
-              <?php e(t('Save')); ?>
-            </button>
-            <?php Session::getCsrfInput(); ?>
-          </form>
-        </details>
-      <?php endif; ?>
-      <hr>
       <?php
       $phone = trim((string) ($values['phone'] ?? ''));
       $fax = trim((string) ($values['fax'] ?? ''));