feat: add page shell, preferences and translations

Base layout with top bar, role-based menu, profile menu and phone layout; theme, language and German form of address kept in cookies; German formal, German informal and English text; Fluent avatar bundled in the image by a Node build stage; placeholder pages for the Publisher and Admin groups.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N3t4WL7bd9bdHHNjEsxzqC

portal/shell/views.py

@@ -0,0 +1,37 @@
+from django.conf import settings
+from django.http import HttpResponseRedirect
+from django.shortcuts import render
+from django.utils.http import url_has_allowed_host_and_scheme
+from django.utils.translation import gettext_lazy as _
+from django.views.decorators.http import require_POST
+
+from portal.accounts.decorators import admin_required, publisher_required
+
+from . import preferences
+
+
+@require_POST
+def set_preferences(request):
+    """Store the chosen preferences in cookies (the no-JavaScript path of the profile menu)."""
+    target = request.POST.get("next", "")
+    if not (target.startswith("/") and url_has_allowed_host_and_scheme(target, None)):
+        target = "/"
+    response = HttpResponseRedirect(target)
+    preferences.set_cookies(
+        response, preferences.chosen(request.POST), secure=not settings.DEBUG
+    )
+    return response
+
+
+def _placeholder(title):
+    def view(request):
+        return render(request, "shell/placeholder.html", {"title": title})
+
+    return view
+
+
+publish_announcements = publisher_required(_placeholder(_("Manage announcements")))
+admin_appearance = admin_required(_placeholder(_("Appearance")))
+admin_settings = admin_required(_placeholder(_("Settings")))
+admin_audit = admin_required(_placeholder(_("Audit log")))
+admin_status = admin_required(_placeholder(_("Status")))