feat(instance): the first start offers instances as tiles

Under the wordmark on a cobalt wash, two tiles as Proton's account page
shows its services: the build's instance, chosen in one tap, and
another, which unfolds the address to type. A ring from cobalt to
copper, a glow and a tagline come in under the pointer, on the
keyboard's focus, while pressed or open; without a mouse the taglines
always show. The launch screen's "Halkyon" over "Learn" becomes
BrandWordmark, which both show.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/lib/l10n/app_localizations_en.dart

@@ -2128,6 +2128,15 @@ class AppLocalizationsEn extends AppLocalizations {
     return 'Use $name';
   }
 
+  @override
+  String get instanceBuiltInTagline => 'Comes with the app';
+
+  @override
+  String get instanceAnother => 'Another instance';
+
+  @override
+  String get instanceAnotherTagline => 'Enter its address';
+
   @override
   String get instanceContinue => 'Continue';