Add admin UI button to clear instance cache

Adds a 'Clear Instance Cache' card to /i/admin/settings/system that POSTs to a CSRF-protected route and calls LandingCacheService::invalidate(), which clears every key behind the landing page, /api/v(1|2)/instance, and nodeinfo.

Useful as an escape hatch after manual ConfigCache edits or when debugging stale-cache symptoms (like trying to set up a brand-new instance); under normal operation the event-driven invalidation in surrounding commits makes this unnecessary.

app/Http/Controllers/Admin/AdminSettingsController.php

@@ -316,6 +316,13 @@ trait AdminSettingsController
         return view('admin.settings.system', compact('sys'));
     }
 
+    public function settingsClearInstanceCache(Request $request)
+    {
+        LandingCacheService::invalidate();
+
+        return redirect()->route('admin.settings.system')->with('status', 'Instance cache cleared.');
+    }
+
     public function settingsApiFetch(Request $request)
     {
         $cloud_storage = ConfigCacheService::get('pixelfed.cloud_storage');

resources/views/admin/settings/system.blade.php

@@ -77,6 +77,22 @@
       </div>
     </div>
   </div>
+  <hr>
+  <p class="h6 text-uppercase text-center">INSTANCE CACHE</p>
+  @if(session('status'))
+  <div class="alert alert-success">{{ session('status') }}</div>
+  @endif
+  <div class="card shadow-none border">
+    <div class="card-body">
+      <p class="mb-2">
+        Clears the cached payloads behind the landing page, <code>/api/v1/instance</code>, <code>/api/v2/instance</code>, and nodeinfo (admin profile, rules, banner blurhash, user and post counts). Safe to run at any time; the values will repopulate on the next request.
+      </p>
+      <form method="POST" action="{{ route('admin.settings.system.clear-instance-cache') }}" class="mb-0">
+        @csrf
+        <button type="submit" class="btn btn-outline-danger font-weight-bold">Clear Instance Cache</button>
+      </form>
+    </div>
+  </div>
 @endsection
 
 @push('styles')

routes/web-admin.php

@@ -64,6 +64,7 @@ Route::domain(config('pixelfed.domain.admin'))->prefix('i/admin')->group(functio
     Route::get('settings/backups', 'AdminController@settingsBackups')->name('admin.settings.backups');
     Route::get('settings/storage', 'AdminController@settingsStorage')->name('admin.settings.storage');
     Route::get('settings/system', 'AdminController@settingsSystem')->name('admin.settings.system');
+    Route::post('settings/system/clear-instance-cache', 'AdminController@settingsClearInstanceCache')->name('admin.settings.system.clear-instance-cache');
 
     Route::get('instances', 'AdminController@instances')->name('admin.instances');
     Route::post('instances', 'AdminController@instanceScan');