AI template generation + per-employee variable rendering

[jusso-dev]

Why

Hoxhunt, Brightside, Proofpoint, Phished all use AI for role-aware personalisation. Static htmlBody/textBody cannot match.

Scope

• New table template_variables linking email_templates to allowed substitutions ({{firstName}}, {{department}}, {{managerFirstName}}, {{recentInternalSender}} etc).
• Server action generateTemplate({ scenario, role, region, language, difficulty }) calling an LLM with strict schema-validated JSON output.
• Preview render against a real employee row before save.
• Provenance: store model id, prompt hash, generated_at on the template row.

Acceptance

• Admin can generate, preview, edit, then save a template.
• Generated templates never leak real employee PII to the model (synthetic samples only).