fix: remove extensive use of any type

[sublime247]

Close #204

• Remove all as any casts in payments.service.ts (lines 117, 169, 276)
• Remove as any cast in auth.service.ts (line 232)
• Remove any parameter type in auth.service.ts generateTokens method
• Create proper PaymentProvider, SubscriptionWebhookEvent, RefundWebhookData interfaces
• Add InvoiceStatus enum to replace inline string union in invoice.entity.ts
• Fix SubscriptionStatus enum usage (use SubscriptionStatus.ACTIVE instead of string cast)
• Fix RefundStatus enum usage (use RefundStatus.PROCESSED instead of string cast)
• Fix cancelAtPeriodEnd column type mismatch in subscription.entity.ts
• Add proper return types to all service and controller methods
• Type webhook service with proper Stripe/PayPal payload interfaces
• Type controller request parameter with AuthenticatedRequest interface
• Add isEmailVerified field to UpdateUserDto to eliminate cast
• Remove duplicate SubscriptionInterval enum from DTO (reuse entity enum)
• Fix JwtStrategy validate method typing and secretOrKey undefined
• Fix transaction.service.ts strict mode errors (unknown error type)
• Fix test/setup.ts global type declaration for strict mode
• Add TransactionService mock to payments.service.spec.ts
• Enable strict TypeScript configuration in tsconfig.json
• Update DTOs to use Record<string, unknown> instead of Record<string, any>

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[sublime247]

@RUKAYAT-CODER please review