chore: rebrand ClubManager -> RosterChief, add lucide icons

The clubmanager.app domain was taken, so the platform is now RosterChief
(rosterchief.app). Renames the Django project package clubmanager/ ->
rosterchief/ (git tracks it as a move, so history follows), every
`from rosterchief.base import ...`, the settings/wsgi/asgi module paths,
env vars (ROSTERCHIEF_BASE_DOMAIN / ROSTERCHIEF_RP_NAME), the MFA adapter
(RosterChiefMFAAdapter), brand text, and the docs.

Two things were deliberately NOT swept:
- club.models.ClubManager stays: it is the Django manager *for Club*, not the
  brand. A blind rename would have silently broken it.
- Migrations are untouched (history is not rewritten). The only reference was a
  cosmetic help_text, so a normal AlterField migration carries the new domain.

Note the WebAuthn RP ID is the base domain, so moving to rosterchief.app
cryptographically invalidates any passkey enrolled under the old one; they
cannot be migrated and must be re-enrolled. Nothing is in production, so the
real cost is zero.

Add django-lucide (from bsiebens/lucide) for icons: the theme toggle now swaps
sun/moon against the effective theme, and the control panel gets icons on its
tabs, actions and stat groups. Its classifiers stop at Django 5.0, but that is
stale metadata — verified rendering on Django 6 / Python 3.14.

Also add formbuilder, shop and controlpanel to ruff's known-first-party list,
which had drifted behind the apps that landed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

club/models.py

@@ -4,8 +4,8 @@ from django.db import models
 from django.utils import timezone
 from django.utils.translation import gettext_lazy as _
 
-from clubmanager.base import ClubScopedModel, UUIDModel, unique_slugify, validate_club_scope
 from members.models import Member
+from rosterchief.base import ClubScopedModel, UUIDModel, unique_slugify, validate_club_scope
 
 
 class ClubManager(models.Manager):
@@ -24,7 +24,7 @@ class ClubManager(models.Manager):
 
 class Club(UUIDModel):
     name = models.CharField(_("name"), max_length=255)
-    slug = models.SlugField(_("slug"), max_length=255, unique=True, blank=True, help_text=_("Drives subdomain / path resolution (e.g. ajax-united.clubmanager.app)."))
+    slug = models.SlugField(_("slug"), max_length=255, unique=True, blank=True, help_text=_("Drives subdomain / path resolution (e.g. ajax-united.rosterchief.app)."))
 
     archived_at = models.DateTimeField(_("archived at"), null=True, blank=True, help_text=_("Archived clubs stop resolving on their subdomain, but their data is retained."))