feat(home): add signup FAB for guest users

[isuri54]

Fixes #

Describe the changes you have made in this PR - -Added a dedicated signup FloatingActionButton(FAB) for guest users -Visible only when (isGuest == true) -Routes to '/auth' on press for seamless onboarding -Positioned at 'Alignment(0.7, -0.8)' to avoid UI clutter

Screenshots of the changes (If any) - Due to a local environmental issue preventing the app from fully building, I couldn't capture actual screenshots. But here's what changed: Before - Guest users had to navigate via logout dialog After - if (localApi.userModel.isGuest == true) FloatingActionButton( onPressed: () => appRouter.pushNamed('/auth'), backgroundColor: kYellow, child: Icon(Icons.login, color: Colors.white), )

Note: Please let me know if screenshots are strictly needed; I can try fixing the build and update later.