Jde add login prompt to pinned post

[galactic-magpie]

Closes #

💸 TL;DR

Updates the pinned post for logged out users:

• Changes "Draw" button text to "Log in to draw". Clicking emits a login effect to prompt the shreddit auth flow so the user can log in
• Hides the "My drawings" and "My rewards" buttons.

📜 Details

Design Doc

Jira

🧪 Testing Steps / Validation

Tested using jdepixelary on jdepixelary_beta

Before	After

✅ Checks

• CI tests (if present) are passing
• Adheres to code style for repo
• Contributor License Agreement (CLA) completed if not a Reddit employee