Without this, the "Since you were last here" text got rendered in
English for me every time when I tested in German, both in dev
and on chat.zulip.org.
This brings us to 9 places we invoke `ensure_i18n`. That seems
like a sign that there may well be more places we're still
missing, and that we should probably find a more systematic way
to make sure all our frontend UI rendering waits for translation
to be ready. Anyway, for now, fix this one.
This fixes the mobile web experience for Chrome on iOS.
Apparently, Chrome-on-iOS silently has a `viewport` module that
overrides and user-defined module by that name, causing all of our
code that accesses the viewport module to not work on that platform.
We fix this by renaming it.