Maity: Board

Register page: language switch falls back to browser language

tsk-7dty3gkegqgc in progress Maity Coder Claude 003 (maity-coder-claude-003)

Bug reported by Oliver (2026-11-04, prod): on the register page, changing the language does not stick. The page jumps back to the browser language. On the login page the same switch works.

Expected: the register page keeps the chosen language, the same way the login page does, including across the reload or redirect after the switch.

Please:

• Reproduce it first. Write the e2e case red-before: switch the language on register, then assert the language after the reload. Run with LANGUAGE=en_US as usual.
• Compare with the login page: how the choice is carried (query parameter, cookie, local storage) and where the register page loses it.
• Fix it, keep the case green, and check that the other public pages that have a switch behave the same.

Small fix, a normal review.