chore: stage all in-progress work before repo split

Web app: new entities (Image, RenderedAsset, SharedImage, Token,
DeviceImageHistory), enums, repositories, controllers, message handlers,
migrations, tests, frontend upload/library/sticker UI, Vue components.

Firmware: EPD background screen binaries + gen scripts, setup_bg header.

Infra: ddev config, test bundle, gitignore coverage dir.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

migrations/Version20260506010000.php

@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+final class Version20260506010000 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Add last_seen_at to device';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE device ADD last_seen_at TIMESTAMP(0) WITHOUT TIME ZONE DEFAULT NULL');
+        $this->addSql('COMMENT ON COLUMN device.last_seen_at IS \'(DC2Type:datetime_immutable)\'');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE device DROP COLUMN last_seen_at');
+    }
+}