Revert "Say that a deploy keeps only an app's volumes when the app has none"

The owner asked for this commit to be reverted in full
(#254 (comment)). It
removes the no-volume-mounts sentence from the app page and the deploy
log, the constant and tests behind it, the README sentence, and its
TODO.md entry. Later TODO.md entries stay. #248
stays closed as rejected.

Model: opus-5-5

TODO.md

@@ -38,11 +38,6 @@ regress.
   style, instead of asking for a container restart, which keeps the old values
   (#255).
 
-- 2026-10-01: An app with no volume mounts says on its page, and in the log of
-  each deploy, that a deploy or rollback loses the files it writes and a restart
-  keeps them; the README's Volume mounts section says a deploy or rollback keeps
-  only the files the app wrote to its volume mounts (#248).
-
 - 2026-10-01: Builds attach a BuildKit session, as the docker command line does,
   so a base image that is not on the host is pulled instead of the build failing
   with "no active sessions" on Docker Engine 27. Container logs, and so the