Improve email verification flow and error handling

- Send verification email before creating user to prevent orphaned accounts
- Detect SMTP authentication errors and fail fast without retries
- Add field-level validation errors for better frontend UX
- Configure docker-compose with explicit environment variables
- Document dollar sign escaping in .env.example (use $$)
- Implement welcome email on successful verification
- Clean up unnecessary comments

.env.example

@@ -1,21 +1,21 @@
 DB_PATH=./data/apocapoc.db
 
 PORT=8080
-HOST=0.0.0.0
+APP_URL=http://localhost:8080
 
 JWT_SECRET=change-me-in-production
 JWT_EXPIRY=1h
 REFRESH_TOKEN_EXPIRY=7d
 
-CORS_ORIGINS=http://localhost:3000
-
 DEFAULT_TIMEZONE=UTC
 
 # Email Configuration (optional - required for email features)
 SMTP_HOST=
 SMTP_PORT=587
 SMTP_USER=
+# Note: Escape $ signs with $$ (e.g., pa$word becomes pa$$word)
 SMTP_PASSWORD=
+SMTP_FROM=noreply@example.com
 
 # Application Branding (optional - override support email if needed)
 SUPPORT_EMAIL=contact@apocapoc.app