feat: add email system with multi-provider support

Implements a comprehensive email system with:
- Multi-provider support (SMTP, SendGrid, Mailgun, Amazon SES)
- Database-stored templates with i18n (EN, FR, DE, LB)
- Jinja2 template rendering with variable interpolation
- Email logging for debugging and compliance
- Debug mode for development (logs instead of sending)
- Welcome email integration in signup flow

New files:
- models/database/email.py: EmailTemplate and EmailLog models
- app/services/email_service.py: Provider abstraction and service
- scripts/seed_email_templates.py: Template seeding script
- tests/unit/services/test_email_service.py: 28 unit tests
- docs/features/email-system.md: Complete documentation

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.env.example

@@ -98,6 +98,39 @@ STRIPE_PUBLISHABLE_KEY=pk_test_your_publishable_key_here
 STRIPE_WEBHOOK_SECRET=whsec_your_webhook_secret_here
 STRIPE_TRIAL_DAYS=30
 
+# =============================================================================
+# EMAIL CONFIGURATION
+# =============================================================================
+# Provider: smtp, sendgrid, mailgun, ses
+EMAIL_PROVIDER=smtp
+EMAIL_FROM_ADDRESS=noreply@wizamart.com
+EMAIL_FROM_NAME=Wizamart
+EMAIL_REPLY_TO=
+
+# SMTP Settings (used when EMAIL_PROVIDER=smtp)
+SMTP_HOST=smtp.example.com
+SMTP_PORT=587
+SMTP_USER=
+SMTP_PASSWORD=
+SMTP_USE_TLS=true
+SMTP_USE_SSL=false
+
+# SendGrid (used when EMAIL_PROVIDER=sendgrid)
+# SENDGRID_API_KEY=SG.your_api_key_here
+
+# Mailgun (used when EMAIL_PROVIDER=mailgun)
+# MAILGUN_API_KEY=your_api_key_here
+# MAILGUN_DOMAIN=mg.yourdomain.com
+
+# Amazon SES (used when EMAIL_PROVIDER=ses)
+# AWS_ACCESS_KEY_ID=your_access_key
+# AWS_SECRET_ACCESS_KEY=your_secret_key
+# AWS_REGION=eu-west-1
+
+# Email behavior
+EMAIL_ENABLED=true
+EMAIL_DEBUG=false
+
 # =============================================================================
 # PLATFORM LIMITS
 # =============================================================================