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>

migrations/Version20260906143919.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Auto-generated Migration: Please modify to your needs!
+ */
+final class Version20260906143919 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Create artwork table (uploaded art + name)';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('CREATE TABLE artwork (id INT AUTO_INCREMENT NOT NULL, name VARCHAR(200) NOT NULL, filename VARCHAR(120) NOT NULL, original_name VARCHAR(255) DEFAULT NULL, mime_type VARCHAR(100) NOT NULL, size INT NOT NULL, uploaded_at DATETIME NOT NULL, PRIMARY KEY (id)) DEFAULT CHARACTER SET utf8mb4 ENGINE = InnoDB');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('DROP TABLE artwork');
+    }
+}