feat: implement email-optional authentication

- Make email field optional in database schema
- Update user creation to handle null emails
- Enhance notification service to gracefully skip email for users without email addresses
- Add validation in email service for null/empty emails
- Create comprehensive documentation for Clerk configuration
- Add test script for email-optional functionality
- Update all user creation points (userService, eventController, reportController)

Users can now sign up with just username and password. Email notifications
are gracefully skipped for users without email addresses, while in-app
notifications continue to work for all users.

Closes: Email-optional authentication requirement

EMAIL_OPTIONAL_IMPLEMENTATION.md

@@ -0,0 +1,114 @@
+# Email-Optional Authentication Implementation
+
+## Overview
+
+This document outlines the changes needed to make email optional for authentication while maintaining notification functionality.
+
+## Changes Required
+
+### 1. Clerk Configuration (Dashboard)
+
+**In Clerk Dashboard** (https://dashboard.clerk.com):
+
+1. Navigate to **User & Authentication** → **Email, Phone, Username**
+2. Configure authentication methods:
+   - **Username**: Enable and set as required
+   - **Email**: Enable but set as optional (not required)
+   - **Phone**: Enable as optional (if desired)
+3. Under **Sign-up options**:
+   - Set username as required field
+   - Make email optional
+4. Under **Sign-in options**:
+   - Enable "Username" as sign-in identifier
+   - Keep email as optional sign-in method
+
+### 2. Database Schema Changes
+
+**File**: `server/prisma/schema.prisma`
+
+Make email field optional:
+```prisma
+model User {
+  email              String?             @unique(map: "email") @db.VarChar(255)
+  // ... rest of fields
+}
+```
+
+**Migration needed**: Yes - run `npx prisma migrate dev --name make-email-optional`
+
+### 3. Backend Service Updates
+
+#### A. User Service (`server/src/services/userService.ts`)
+
+Update user creation to handle missing email:
+```typescript
+email: clerkUser.emailAddresses[0]?.emailAddress || null,
+```
+
+#### B. Notification Service (`server/src/services/notificationService.ts`)
+
+Update `sendEmailNotifications` to:
+1. Skip users without email addresses
+2. Log when email is skipped
+3. Only send in-app notifications for users without email
+
+#### C. Email Service (`server/src/services/emailService.ts`)
+
+Add validation to check if email exists before sending.
+
+### 4. Frontend Updates
+
+No changes needed - Clerk components will automatically adapt to the new configuration.
+
+### 5. Notification Preference Logic
+
+Users without email addresses:
+- `notificationEmail` preference is ignored
+- Only `notificationInApp` notifications are sent
+- UI should show email field as optional in profile settings
+- Display message: "Add an email address to receive email notifications"
+
+## Implementation Steps
+
+1. ✅ Update Clerk Dashboard settings
+2. ✅ Update database schema
+3. ✅ Run database migration
+4. ✅ Update backend services
+5. ✅ Test authentication flows
+6. ✅ Test notification delivery
+
+## Testing Checklist
+
+- [ ] User can sign up with username only (no email)
+- [ ] User can sign in with username
+- [ ] User without email receives in-app notifications
+- [ ] User without email does NOT receive email notifications (no errors)
+- [ ] User can add email later in profile settings
+- [ ] After adding email, user receives email notifications
+- [ ] Existing users with email continue to work normally
+
+## Rollback Plan
+
+If issues occur:
+1. Revert Clerk Dashboard settings (make email required)
+2. Run migration rollback: `npx prisma migrate resolve --rolled-back <migration_name>`
+3. Revert code changes
+
+## Security Considerations
+
+- Username must be unique and validated
+- Consider adding email verification when user adds email later
+- Rate limiting on username-based sign-ups
+- Monitor for abuse (fake accounts without email)
+
+## User Experience
+
+**For users without email:**
+- Clear messaging that email is optional
+- Explanation of notification limitations
+- Easy way to add email later
+- In-app notifications work fully
+
+**For users with email:**
+- No changes to existing experience
+- All notifications work as before