fix: language switch losing prefix + SSL redirect scheme

Menu links used url= which doesn't prepend language prefix.
Changed to pageRef= which resolves per-language correctly.

Also fixed root redirect using http:// instead of https://
by reading X-Forwarded-Proto from gateway proxy.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

config/_default/languages.de.toml

@@ -28,23 +28,23 @@ contentDir = "content/de"
 [[menus.main]]
   identifier = "about"
   name = "Über uns"
-  url = "/about/"
+  pageRef = "/about"
   weight = 2
 
 [[menus.main]]
   identifier = "tags"
   name = "Themen"
-  url = "/tags/"
+  pageRef = "/tags"
   weight = 3
 
 [[menus.footer]]
   identifier = "impressum"
   name = "Impressum"
-  url = "/impressum/"
+  pageRef = "/impressum"
   weight = 1
 
 [[menus.footer]]
   identifier = "privacy"
   name = "Datenschutzerklärung"
-  url = "/datenschutz/"
+  pageRef = "/datenschutz"
   weight = 2

config/_default/languages.en.toml

@@ -28,23 +28,23 @@ contentDir = "content/en"
 [[menus.main]]
   identifier = "about"
   name = "About"
-  url = "/about/"
+  pageRef = "/about"
   weight = 2
 
 [[menus.main]]
   identifier = "tags"
   name = "Topics"
-  url = "/tags/"
+  pageRef = "/tags"
   weight = 3
 
 [[menus.footer]]
   identifier = "impressum"
   name = "Imprint"
-  url = "/imprint/"
+  pageRef = "/imprint"
   weight = 1
 
 [[menus.footer]]
   identifier = "privacy"
   name = "Privacy Policy"
-  url = "/privacy/"
+  pageRef = "/privacy"
   weight = 2

config/_default/languages.fr.toml

@@ -28,23 +28,23 @@ contentDir = "content/fr"
 [[menus.main]]
   identifier = "about"
   name = "À propos"
-  url = "/about/"
+  pageRef = "/about"
   weight = 2
 
 [[menus.main]]
   identifier = "tags"
   name = "Sujets"
-  url = "/tags/"
+  pageRef = "/tags"
   weight = 3
 
 [[menus.footer]]
   identifier = "impressum"
   name = "Mentions légales"
-  url = "/mentions-legales/"
+  pageRef = "/mentions-legales"
   weight = 1
 
 [[menus.footer]]
   identifier = "privacy"
   name = "Politique de confidentialité"
-  url = "/politique-de-confidentialite/"
+  pageRef = "/politique-de-confidentialite"
   weight = 2