Serve plain HTTP only and drop the local certificate tooling

The app never terminates TLS: a reverse proxy or tunnel does, and
isSecureRequest still reads X-Forwarded-Proto so cookies stay Secure.
Removes the cert generator, TLS resolution and HTTP redirect, the
local CA download, and the TLS envs, and trims the installer, Dockerfile
health check and docs to match. Also softens the composer's loading row.

RELEASING.md

@@ -61,11 +61,9 @@ Before the first public release:
 - [ ] The GHCR package is public.
 - [ ] The first release is installed on the real host and a signup, a chat
       reply, a computer and a routine have been exercised.
-- [ ] A plain `curl | bash` install ends on `https://`, `/ca.crt`
-      downloads, and a device that trusted the CA installs the app, gets a
-      live chat socket and can turn on notifications.
-- [ ] `--no-https` behind a proxy, and `--https-cert`/`--https-key` with a
-      real certificate, were each tried once.
+- [ ] A plain `curl | bash` install answers on `http://<host>:7227`, and
+      the same install behind a reverse proxy serves HTTPS, installs the
+      app, gets a live chat socket and can turn on notifications.
 
 ## Rollback