Fix infinite redirect loop on omsorgWeb behind the TLS-terminating proxy

The root .htaccess forces HTTPS via `RewriteCond %{HTTPS} !=on`. Behind a
reverse proxy that terminates TLS and forwards to Apache over plain HTTP,
%{HTTPS} is always "off" - verified via mod_rewrite trace logging that
this is NOT spoofable via SetEnvIf or a RewriteRule E-flag, despite that
being commonly recommended; %{HTTPS} reflects only the actual TLS
connection to Apache. Every request was therefore redirected to https://,
which the proxy forwarded back over HTTP, looping forever (browser: "the
page isn't redirecting properly").

Fix: .htaccess's redirect condition also accepts a trusted
X-Forwarded-Proto: https header as evidence the request is already
HTTPS. omsorgWeb/docker/000-default.conf additionally sets HTTPS=on in
the request environment when that header is present, so mod_headers'
`env=HTTPS` condition (HSTS header) still fires correctly - this part
doesn't affect mod_rewrite's %{HTTPS} but is unrelated to the redirect fix.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

omsorgWeb/Dockerfile

@@ -14,6 +14,12 @@ RUN apt-get update \
 COPY omsorgWeb/docker/allow-htaccess.conf /etc/apache2/conf-available/allow-htaccess.conf
 RUN a2enconf allow-htaccess
 
+# Ersetzt die mitgelieferte Default-vhost (identisch, nur mit einer zusätzlichen Rewrite-Regel,
+# die den TLS-terminierenden Host-nginx davor erkennt - sonst redirected die root-.htaccess
+# endlos, siehe Datei-Kommentar. Muss im <VirtualHost>-Block selbst stehen, ein conf-enabled-Drop-in
+# außerhalb davon wird nicht mit der .htaccess desselben Pfads zusammengeführt.)
+COPY omsorgWeb/docker/000-default.conf /etc/apache2/sites-enabled/000-default.conf
+
 COPY omsorgWeb/ /var/www/html/
 COPY .htaccess /var/www/html/.htaccess