Handle coagulate links

[LGro]

Guides iOS: https://docs.flutter.dev/cookbook/navigation/set-up-universal-links Android: https://docs.flutter.dev/cookbook/navigation/set-up-app-links

Tasks

• [x] wellknown file for coagulate.social
• [x] add router to app
• [x] update xcode project as necessary including the right capabilities
• [x] updatie the android app manifest accordingly
• [x] host assetlinks.json on coagulate.social
• [x] figure our how to handle the fragment, consider using https://pub.dev/packages/uni_links and see https://docs.flutter.dev/ui/navigation/deep-linking
• [ ] handle malformed links gracefully with a helpful error message (currently showing "GoException: no routes for location" for /c on iOS and for malformed /en/c#123 goes to qr code scanning mode)

[LGro]

assetlinks.json ist just missing the hash, which can be computed with

keytool -list -v -keystore <path-to-keystore>

[LGro]

plist.info is still missing the flutter deeplink key

[LGro]

Android does not seem to be handling app links at all at the moment.