Fix unauthenticated fallback to user ID 1 in postcard flows

[mlintangmz2765]

Motivation

• Prevent accidental reads/writes into user ID 1 when the auth state is missing, which could produce data leakage between users.
• Ensure postcard/contact operations require an authenticated user rather than silently using a default fallback.

Description

• Removed the auth()->id() ?? 1 fallback and changed writes to use auth()->id() directly in RegisterPostcard and EditPostcard.
• Added explicit auth guard checks with abort_unless($userId, 403) in RegisterPostcard::mount() and updatedNamaKontak() to reject unauthenticated access early.
• Updated Contact::updateOrCreate() and Postcard::create() usages to store the authenticated user ID and changed the Edit flow contact update to stop falling back to 1.

Testing

• Ran syntax checks with php -l app/Livewire/RegisterPostcard.php and php -l app/Livewire/EditPostcard.php, both succeeded.
• Attempted to run the test suite with php artisan test, but dependency installation failed due to network/proxy errors when Composer attempted to fetch packages, so the full test run could not be executed.

---

Codex Task