fix(auth): ensure “Sign Up” button remains visible on short viewports (100svh + overflow-y-auto)

[Hritwik001]

## ✨ Summary

Fixed an issue where the “Sign Up” button on the “Almost there!” onboarding page was partially hidden on short viewport heights (e.g., small laptops, split-screen, or mobile browsers).

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## 🧠 Root Cause

The outer wrapper used a fixed h-screen height without vertical scrolling. When the viewport height shrank below ~700 px, the button was clipped and inaccessible.

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## 🛠️ Fix

• Replaced h-screen with min-h-[100svh] for correct small-viewport behavior.
• Added overflow-y-auto to enable vertical scrolling when content exceeds viewport height.

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## ✅ Testing

• Verified build passes (npm run build).
• Verified visually on Chrome (Windows 11) at 600–1080 px height.
• “Sign Up” CTA is now always visible and clickable.
• No layout shift or horizontal scroll introduced.

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## 🔗 Closes

Fixes #4698 : https://github.com/Infisical/infisical/issues/4698

[maidul98]

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[Hritwik001]

Hi 👋, this PR fixes the issue where the “Sign Up” button on the “Almost there!” screen was getting cut off on smaller screens.

Fix Summary

• Replaced h-screen with min-h-[100svh]
• Added overflow-y-auto so the page can scroll properly

Tested at different screen heights (600–1080 px).
The “Sign Up” button is now fully visible and clickable. ✅

Happy to make any adjustments if needed. 🙌