feat: add EventReferral node type definition

[pyramation]

Summary

Adds the EventReferral node type definition to the node-type-registry. EventReferral is a sibling to EventTracker — it watches any table for DML events and records events attributed to the referrer (inviter) by automatically looking up claimed_invites from the membership_type context.

Parameter schema:

• event_name (required) — event type name to record for the referrer
• events — DML events to watch (default: ['INSERT'])
• actor_field — column containing the invitee ID (default: owner_id)
• entity_field — optional column for entity-scoped referral events
• auto_register_type — auto-register in event_types (default: true)
• conditions / condition_field / watch_fields — same compound condition support as EventTracker

Companion PR in constructive-db implements the SQL generator and wiring.

Refs #877

Review & Testing Checklist for Human

Risk: 🟢 Low — additive change, new file + one export line

• Verify EventReferral parameter schema matches what the SQL generator in constructive-db expects
• Confirm conditionProperties spread correctly includes condition_field, condition_value, conditions, watch_fields

Notes

• No runtime behavior change — this is purely a TypeScript definition consumed by the seed generator
• The conditionDefs/conditionProperties are shared with EventTracker and JobTrigger

Link to Devin session: https://app.devin.ai/sessions/e0a3f1cfea6e4e809160c9d0cd755b90
Requested by: @pyramation

[devin-ai-integration]

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