Most Recent Webxdc apps but make it a widget

[zeitschlag]

This PR adds a Widget to Deltachat. The widget shows the most recent Webxdc-apps on the Homescreen so that users can open them right away from the Homescreen. It comes in two flavours/sizes:

• small. Shows up to 4 apps.
• medium. Shows up to 8 apps.

They look like this:

When users tap on an icon, the selected app opens right away in the right chat. The list gets updated every 15 minutes.

When adding them to the Homescreen, users see this:

The icons for this placeholder come from various Webxdc-app-repos.

Also: This PR makes CI use Xcode 16. And closes #2406
Sidenote: Widgets are more fun on an actual device than in the Simulator.
Sidenote: Widget is not localized yet.

[r10s]

wow! that already looks great!

also nice, that the appicon can be changed to a widget by just long-tapping, did not know about that, is that new in iOS 18? a bit confusing might be that the app icon is lost by that, but the user can undo the same way or re-add that as usual, this is also OS part, there is probably not much we can do about that.

i know, this is a draft, however, some random comments: i think, there are only few steps needed to have "something" that can be shipped:

• having a method to somehow "add" a webxdc so that it is always shown. we may revive the old "Add To Home Screen" option inside a webxdc for that. once tapped, it will get its place atop of the list, maybe including some hints how to add the widget (or can we trigger that from the app even?

• explicitly added ones may come from any accounts, meaning that each webxdc in the starer-widget may belong to a different account

"removing" is not needed for the start, the list is anyways filled with the recent ones, when more webxdc are added than can be shown, the last are not shown. that's fine to start with

also, it seems fine to fill the recents from the "current" account (i think, this is what happens currently). also fine is to have only one widget, things otherwise gets confusing and also more complicated implementation-wise

[r10s]

this can be removed, encrypted accounts are deprecated at #2011, also in the newer DcNotificationService we do not care for encrypted accounts

Suggested change

	for accountId in dcAccounts.getAll() {
	let dcContext = dcAccounts.get(id: accountId)
	if dcContext.isOpen() == false {
	do {
	let secret = try KeychainManager.getAccountSecret(accountID: accountId)
	_ = dcContext.open(passphrase: secret)
	} catch {
	debugPrint("Couldn't open \(error.localizedDescription)")
	}
	}
	}

[zeitschlag]

Ah, that's good to know, thank you!
I basically just copied this from AppDelegate.continueDidFinishLaunchingWithOptions. Should we remove it there as well?