feat: Phase 1+2 - JWT auth, dashboard metrics API, DB indexes

Phase 1 - JWT Auth Foundation:
- Replace token auth with djangorestframework-simplejwt
- POST /api/v1/admin/auth/login/ - returns access + refresh JWT
- POST /api/v1/auth/refresh/ - JWT refresh
- GET /api/v1/auth/me/ - current admin profile
- GET /api/v1/health/ - DB health check
- Add ledger app to INSTALLED_APPS

Phase 2 - Dashboard Metrics API:
- GET /api/v1/dashboard/metrics/ - revenue, partners, events, tickets
- GET /api/v1/dashboard/revenue/ - 7-day revenue vs payouts chart data
- GET /api/v1/dashboard/activity/ - last 10 platform events feed
- GET /api/v1/dashboard/actions/ - KYC queue, flagged events, pending payouts

DB Indexes (dashboard query optimisation):
- RazorpayTransaction: status, captured_at
- Partner: status, kyc_compliance_status
- Event: event_status, start_date, created_date
- Booking: created_date
- PaymentTransaction: payment_type, payment_transaction_status, payment_transaction_date

Infra:
- Add Dockerfile for eventify-backend container
- Add simplejwt to requirements.txt
- All 4 dashboard views use IsAuthenticated permission class

banking_operations/models.py

@@ -44,7 +44,7 @@ class PaymentGatewayCredentials(models.Model):
 
 class PaymentTransaction(models.Model):
     payment_transaction_id = models.CharField(max_length=250)
-    payment_type = models.CharField(max_length=250, choices=[
+    payment_type = models.CharField(max_length=250, db_index=True, choices=[
         ('credit', 'Credit'),
         ('debit', 'Debit'),
         ('transfer', 'Transfer'),
@@ -58,14 +58,14 @@ class PaymentTransaction(models.Model):
     payment_gateway = models.ForeignKey(PaymentGateway, on_delete=models.CASCADE)
     payment_transaction_amount = models.DecimalField(max_digits=10, decimal_places=2)
     payment_transaction_currency = models.CharField(max_length=10)
-    payment_transaction_status = models.CharField(max_length=250, choices=[
+    payment_transaction_status = models.CharField(max_length=250, db_index=True, choices=[
         ('pending', 'Pending'),
         ('completed', 'Completed'),
         ('failed', 'Failed'),
         ('refunded', 'Refunded'),
         ('cancelled', 'Cancelled'),
     ])
-    payment_transaction_date = models.DateField(auto_now_add=True)
+    payment_transaction_date = models.DateField(auto_now_add=True, db_index=True)
     payment_transaction_time = models.TimeField(auto_now_add=True)
     payment_transaction_notes = models.TextField(blank=True, null=True)
     payment_transaction_raw_data = models.JSONField(blank=True, null=True)