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>

.env.test

@@ -1,3 +1,7 @@
 # define your env variables for the test env here
 KERNEL_CLASS='App\Kernel'
 APP_SECRET='$ecretf0rt3st'
+MESSENGER_TRANSPORT_DSN=in-memory://
+SHARE_TOKEN_TTL_DAYS=7
+HARD_DELETE_TOKEN_TTL_DAYS=30
+MAILER_SENDER=noreply@test.example