Fix test failures: GoRouter context error and bottom action bar overflow

[Copilot]

Tests were failing due to GoRouter.of(context) being called in a test environment without a router, and the new My Festival action buttons causing a 85px overflow in the bottom action bar.

GoRouter Context Handling

Changed _handlePostInitRedirect() in lib/main.dart to use GoRouter.maybeOf() and return early when no router is available (e.g., in test environments):

final router = GoRouter.maybeOf(context);
if (router == null) {
  return;
}

Bottom Action Bar Layout

• Wrapped actions in Expanded widgets to distribute horizontal space evenly
• Added text overflow handling to ActionButton labels (overflow: TextOverflow.ellipsis, maxLines: 1)
• Updated golden files for screenshot tests to reflect the constrained layout

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