This commit moves the placeholder elements for the message edit form,
to `message_edit_form.hbs`, so they are conditionally rendered only
when a message is being edited, rather than being present for every
message in the list.
Fixes#31134.
Ever since we started bundling the app with webpack, there’s been less
and less overlap between our ‘static’ directory (files belonging to
the frontend app) and Django’s interpretation of the ‘static’
directory (files served directly to the web).
Split the app out to its own ‘web’ directory outside of ‘static’, and
remove all the custom collectstatic --ignore rules. This makes it
much clearer what’s actually being served to the web, and what’s being
bundled by webpack. It also shrinks the release tarball by 3%.
Signed-off-by: Anders Kaseorg <anders@zulip.com>