feat: add AirShelf core implementation

core/backend/apps/accounts/admin.py

@@ -0,0 +1,25 @@
+from django.contrib import admin
+from django.contrib.auth.admin import UserAdmin
+
+from .models import Team, TeamMember, User
+
+
+@admin.register(User)
+class AirShelfUserAdmin(UserAdmin):
+    list_display = ("username", "email", "status", "is_staff", "date_joined")
+    list_filter = ("status", "is_staff", "is_superuser")
+
+
+@admin.register(Team)
+class TeamAdmin(admin.ModelAdmin):
+    list_display = ("name", "owner", "status", "created_at")
+    search_fields = ("name", "owner__username", "owner__email")
+    list_filter = ("status",)
+
+
+@admin.register(TeamMember)
+class TeamMemberAdmin(admin.ModelAdmin):
+    list_display = ("team", "user", "role", "status", "monthly_credit_limit")
+    search_fields = ("team__name", "user__username", "user__email")
+    list_filter = ("role", "status")
+