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>

templates/emails/share_notification.txt.twig

@@ -0,0 +1,9 @@
+{{ sharer.email }} shared a photo with you on pictureFrame.
+
+Add to my frame:
+{{ absolute_url('/token/' ~ approveToken.uuid ~ '/approve') }}
+
+No thanks (decline):
+{{ absolute_url('/token/' ~ declineToken.uuid ~ '/decline?back=' ~ approveToken.uuid) }}
+
+These links expire in {{ (approveToken.expiresAt.timestamp - 'now'|date('U')) // 86400 }} days.