fix: Resolve TypeScript errors and apply database migration for email-optional

- Add Prisma import for JsonNull filter
- Fix async/await for calculateDistance function
- Install mysql2 for database operations
- Apply ALTER TABLE migration to make email nullable in database
- Verify all tests pass successfully

Tests confirm:
- Users can be created without email
- Notifications work for users without email
- Email sending gracefully skipped when no email present
- Database queries correctly filter by email presence

server/src/services/notificationService.ts

@@ -1,4 +1,5 @@
 import prisma from '../config/database';
+import { Prisma } from '@prisma/client';
 import { calculateDistance } from '../utils/spatial';
 import { emailService } from './emailService';
 
@@ -55,7 +56,7 @@ export class NotificationService {
           { notificationInApp: true },
         ],
         areasOfInterest: {
-          not: null,
+          not: Prisma.JsonNull,
         },
       },
       select: {
@@ -77,7 +78,7 @@ export class NotificationService {
 
         // Check if the location falls within any of the user's areas of interest
         for (const area of areasOfInterest) {
-          const distance = calculateDistance(
+          const distance = await calculateDistance(
             latitude,
             longitude,
             area.lat,