feat: Quota overage system, updated tier pricing, and communication addons

Quota Overage System:
- Add QuotaOverage model for tracking resource/user quota overages
- Implement 30-day grace period with email notifications (immediate, 7-day, 1-day)
- Add QuotaWarningBanner component in BusinessLayout
- Add QuotaSettings page for managing overages and archiving resources
- Add Celery tasks for automated quota checks and expiration handling
- Add quota management API endpoints

Updated Tier Pricing (Stripe: 2.9% + $0.30):
- Free: No payments (requires addon)
- Starter: 4% + $0.40
- Professional: 3.5% + $0.35
- Business: 3.25% + $0.32
- Enterprise: 3% + $0.30

New Subscription Addons:
- Online Payments ($5/mo + 5% + $0.50) - for Free tier
- SMS Notifications ($10/mo) - enables SMS reminders
- Masked Calling ($15/mo) - enables anonymous calling

BusinessEditModal Improvements:
- Increased width to match PlanModal (max-w-3xl)
- Added all tier options with auto-update on tier change
- Added limits configuration and permissions sections

Backend Fixes:
- Fixed SubscriptionPlan serializer to include all communication fields
- Allow blank business_tier for addon plans
- Added migration for business_tier field changes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/src/types.ts

@@ -93,6 +93,17 @@ export interface NotificationPreferences {
   marketing: boolean;
 }
 
+export interface QuotaOverage {
+  id: number;
+  quota_type: string;
+  display_name: string;
+  current_usage: number;
+  allowed_limit: number;
+  overage_amount: number;
+  days_remaining: number;
+  grace_period_ends_at: string;
+}
+
 export interface User {
   id: string | number;
   username?: string;
@@ -109,6 +120,7 @@ export interface User {
   can_invite_staff?: boolean;
   can_access_tickets?: boolean;
   permissions?: Record<string, boolean>;
+  quota_overages?: QuotaOverage[];
 }
 
 export type ResourceType = 'STAFF' | 'ROOM' | 'EQUIPMENT';