Declare `target` as a datetime widget in signage-app.json

[vpetersson]

Summary

The app store now renders a proper native date & time picker for manifest settings fields that ask for one, but Timer's manifest still declares target as a plain text box, so the store shows a bare text input where the user has to hand-type ISO 8601.

The store-side renderer support has already landed in Screenly-Labs/app-store (config-manifest.js supports x-widget: date|time|datetime, also inferred from JSON Schema format). This ticket is the one-field change needed here, on the origin manifest, so the picker actually appears.

Change

In .well-known/signage-app.json, update the target property:

"target": {
  "type": "string",
  "title": "Target date & time",
  "description": "A future target counts down; a past one counts up. The value is read in the time zone below (or its own offset if you paste one in).",
  "format": "date-time",
  "x-widget": "datetime"
}

• Add "x-widget": "datetime" (and, for standards-compliance, "format": "date-time").
• The picker's value is ISO 8601 (YYYY-MM-DDTHH:MM:SS) — the same shape the app already parses, so no player-side change is needed.

Notes

• Widget vocabulary is documented in the app-store repo: docs/app-manifest.md (date / time / datetime).
• Once this deploys and the origin serves the datetime widget, no store-side override is needed (none was added).

Filed from the app-store while fixing the date/time picker regression.