Add backlogger app at /backlogger/ with login protection

Django app with Item model (games/books/films/other categories), CRUD
views, and login-required access. Login page at /accounts/login/ uses
custom dark-themed template consistent with the site design.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backlogger/admin.py

@@ -0,0 +1,9 @@
+from django.contrib import admin
+from .models import Item
+
+
+@admin.register(Item)
+class ItemAdmin(admin.ModelAdmin):
+    list_display = ['name', 'category', 'progress_percent', 'favorite', 'created_at']
+    list_filter = ['category', 'favorite']
+    search_fields = ['name']