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/menu.py

@@ -0,0 +1,61 @@
+"""The left menu, declared once. An entry is shown only to users who may open its page."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from django.urls import reverse
+from django.utils.translation import gettext_lazy as _
+
+
+@dataclass(frozen=True)
+class Entry:
+    label: object  # lazy translated string
+    url_name: str
+
+
+@dataclass(frozen=True)
+class Group:
+    title: object | None
+    role: str | None  # None: everyone; otherwise "publisher" or "admin"
+    entries: tuple[Entry, ...]
+
+
+MENU = (
+    Group(None, None, (Entry(_("Home"), "home"),)),
+    Group(
+        _("Publishing"),
+        "publisher",
+        (Entry(_("Manage announcements"), "publish-announcements"),),
+    ),
+    Group(
+        _("Administration"),
+        "admin",
+        (
+            Entry(_("Appearance"), "admin-appearance"),
+            Entry(_("Settings"), "admin-settings"),
+            Entry(_("Audit log"), "admin-audit"),
+            Entry(_("Status"), "admin-status"),
+        ),
+    ),
+)
+
+
+def _allowed(group: Group, portal_user) -> bool:
+    if group.role is None:
+        return True
+    return bool(getattr(portal_user, f"is_{group.role}", False))
+
+
+def for_user(portal_user, current_path: str) -> list[dict]:
+    """The groups this user sees, each entry with its address and whether it is current."""
+    groups = []
+    for group in MENU:
+        if not _allowed(group, portal_user):
+            continue
+        entries = []
+        for entry in group.entries:
+            url = reverse(entry.url_name)
+            entries.append({"label": entry.label, "url": url, "current": url == current_path})
+        groups.append({"title": group.title, "entries": entries})
+    return groups