Remove dry-run feature and update email configuration

Changes:
- Remove DRY_RUN environment variable and --dry-run CLI flag
- Always send emails directly without preview mode
- Update sender email to x-news@ksalk.pl
- Remove dry run config from types, env schema, and email service

Email now successfully sends to konrad.salkowski@gmail.com from x-news@ksalk.pl

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

.env.example

@@ -29,7 +29,7 @@ BREVO_SMTP_HOST=smtp-relay.brevo.com
 BREVO_SMTP_PORT=587
 BREVO_SMTP_USER=9faa1f001@smtp-brevo.com
 BREVO_SMTP_KEY=your-brevo-smtp-api-key
-EMAIL_FROM_ADDRESS=newsletter@yourdomain.com
+EMAIL_FROM_ADDRESS=x-news@ksalk.pl
 EMAIL_FROM_NAME=Daily Tech Digest
 # Comma-separated recipient list
 EMAIL_RECIPIENTS=you@example.com
@@ -48,5 +48,3 @@ CRON_TIMEZONE=Europe/Warsaw
 ENABLE_AI_SUMMARIES=true
 INCLUDE_RETWEETS=false
 INCLUDE_REPLIES=false
-# Set true to skip email sending (for testing)
-DRY_RUN=false