feat(system): daily security summary email template

[pigri]

Summary

New system workflow template: daily-stats-email — emails each workspace a daily summary of blocked traffic.

• Trigger: event on the daily_stats Kafka topic (produced by the ax_prod pg_cron job daily_block_stats() via pg_net → Strimzi Kafka Bridge), scope: workspace.
• Steps: data.template (renders the stats — totals + day-over-day, by-action, top rules/countries/ASNs, unique IPs — into an HTML body) → resend.email (branded card).
• Recipients: ${variables.email_recipients} — set per tenant at install (identity/email isn't in the platform DB).

Requirements

• workflow-service ≥ the build that adds the data.template node (pigri/arxignis#735, deployed).
• The daily_stats topic + daily_block_stats() function (shipped in pigri/arxignis#735).
• Per-tenant install must set the email_recipients variable.

Notes

• The template's HTML is rendered with data.template in html mode, so traffic-derived fields (rule names, etc.) are auto-escaped — verified against a malicious <b> rule name.
• Numbers use {{printf "%.0f" .n}} to render counts as integers.