ENG-9809: Make sign in button reditect to login

[carlosabadia]

No description provided.

[linear-code]

ENG-9809

[greptile-apps]

Greptile Summary

This PR redirects the "Sign In" button in both the marketing navbar and the mobile sidebar drawer to a dedicated /login page instead of the build root URL. It also reshuffles the responsive visibility logic in the desktop nav — the max-xl:hidden class moves from the Sign In item to the Book a Demo item, and the dual-span label pattern on "Book a Demo" is simplified to a plain string.

• REFLEX_BUILD_LOGIN_URL is cleanly derived from REFLEX_BUILD_URL at import time using .rstrip('/'), correctly handling both slash-suffixed and bare env-var values.
• Both Sign In entry points (desktop navbar and mobile drawer footer) are updated consistently.
• The responsive-visibility swap means Sign In is now always shown in the desktop nav while Book a Demo is hidden below xl breakpoint.

Confidence Score: 5/5

Safe to merge — the change is a straightforward URL update with a correctly constructed constant and consistent application across both navbar and sidebar.

The constant derivation handles both trailing-slash and no-trailing-slash env-var values correctly, both Sign In surfaces are updated together, and the responsive-visibility refactor in the navbar is a clean simplification with no logic risk.

No files require special attention.

Important Files Changed

Filename	Overview
packages/reflex-site-shared/src/reflex_site_shared/constants.py	Adds REFLEX_BUILD_LOGIN_URL derived from REFLEX_BUILD_URL with correct rstrip handling; clean constant extraction.
packages/reflex-site-shared/src/reflex_site_shared/views/marketing_navbar.py	Sign In button href updated to REFLEX_BUILD_LOGIN_URL; responsive visibility class swapped from Sign In item to Book a Demo item, and the dual-span pattern replaced with a single string.
packages/reflex-site-shared/src/reflex_site_shared/views/sidebar/init.py	Drawer footer Sign In button href updated from REFLEX_BUILD_URL to REFLEX_BUILD_LOGIN_URL; consistent with navbar change.

_{Reviews (1): Last reviewed commit: "ENG-9809: Make sign in button reditect t..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing carlos/update-sign-in-redirect (8e50c22) with main (932f20f)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩