Build authentication pages (Login, Sign Up, Forgot Password) with form validation #21

📋 Description

Create the full authentication page set and client-side validation flows to support account access and recovery.

✅ Acceptance Criteria

• Login page supports email/password with inline validation.
• Sign up page supports required registration fields with validation feedback.
• Forgot password page supports recovery request submission.
• Validation messages are clear and localized-ready.
• Error and loading states are visible on all three pages.

🔗 Prerequisite Issues

DoD

• All auth pages are routable and integrated in app navigation.
• Validation blocks invalid submit attempts.
• Basic accessibility checks pass (labels, focus order, keyboard use).
• Screens are reviewed and approved against UI baseline.