Add Art section: upload named images, gallery, delete

- Artwork entity (name, stored filename, original name, mime, size, date)
- /art gallery grid; /art/upload (name + image file, PNG/JPEG/GIF/WebP,
  20M cap); /art/{id}/file streams the image behind auth; /art/{id}/delete
  (CSRF) removes row + file
- files stored under var/uploads/art/ (git-ignored, on the php_var volume
  in Docker), served through a controller so they stay login-gated
- "Art" nav item

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

src/Form/ArtworkType.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace App\Form;
+
+use App\Entity\Artwork;
+use Symfony\Component\Form\AbstractType;
+use Symfony\Component\Form\Extension\Core\Type\FileType;
+use Symfony\Component\Form\Extension\Core\Type\TextType;
+use Symfony\Component\Form\FormBuilderInterface;
+use Symfony\Component\OptionsResolver\OptionsResolver;
+use Symfony\Component\Validator\Constraints\Image;
+use Symfony\Component\Validator\Constraints\NotNull;
+
+class ArtworkType extends AbstractType
+{
+    public function buildForm(FormBuilderInterface $builder, array $options): void
+    {
+        $builder
+            ->add('name', TextType::class, [
+                'help' => 'Shown in the gallery.',
+            ])
+            ->add('file', FileType::class, [
+                'label' => 'Image file',
+                'mapped' => false,
+                'constraints' => [
+                    new NotNull(message: 'Please choose an image.'),
+                    new Image(
+                        maxSize: '20M',
+                        mimeTypes: ['image/png', 'image/jpeg', 'image/gif', 'image/webp'],
+                        mimeTypesMessage: 'Upload a PNG, JPEG, GIF or WebP image.',
+                    ),
+                ],
+            ]);
+    }
+
+    public function configureOptions(OptionsResolver $resolver): void
+    {
+        $resolver->setDefaults(['data_class' => Artwork::class]);
+    }
+}