feat: Datafields page, merge fee types into membership_fee_settings, sidebar

- Add /admin/datafields (DatafieldsLive) for member and custom field config
- Remove Memberdata block from GlobalSettingsLive
- Router: drop /membership_fee_types, add new_fee_type and edit_fee_type under membership_fee_settings
- MembershipFeeSettingsLive: fee types table, collapsible examples; Index links updated
- PagePaths: admin_datafields, admin_import; remove membership_fee_types
- Sidebar: order and labels (Basic settings, Datafields, Membership fee settings, Import, Users, Roles)
- Gettext: German translations for sidebar and OIDC
- Tests: datafields and fee routes, permission and form tests updated

lib/mv_web/page_paths.ex

@@ -8,30 +8,30 @@ defmodule MvWeb.PagePaths do
 
   # Sidebar top-level menu paths
   @members "/members"
-  @membership_fee_types "/membership_fee_types"
   @statistics "/statistics"
 
   # Administration submenu paths (all must match router)
   @users "/users"
   @groups "/groups"
   @admin_roles "/admin/roles"
+  @admin_datafields "/admin/datafields"
   @membership_fee_settings "/membership_fee_settings"
+  @admin_import "/admin/import"
   @settings "/settings"
 
   @admin_page_paths [
     @users,
     @groups,
     @admin_roles,
+    @admin_datafields,
     @membership_fee_settings,
+    @admin_import,
     @settings
   ]
 
   @doc "Path for Members index (sidebar and page permission check)."
   def members, do: @members
 
-  @doc "Path for Membership Fee Types index (sidebar and page permission check)."
-  def membership_fee_types, do: @membership_fee_types
-
   @doc "Path for Statistics page (sidebar and page permission check)."
   def statistics, do: @statistics
 
@@ -41,6 +41,8 @@ defmodule MvWeb.PagePaths do
   def users, do: @users
   def groups, do: @groups
   def admin_roles, do: @admin_roles
+  def admin_datafields, do: @admin_datafields
   def membership_fee_settings, do: @membership_fee_settings
+  def admin_import, do: @admin_import
   def settings, do: @settings
 end