feat: admin email hub — sent log, inbox, compose, audiences, delivery tracking

Add full email management at /admin/emails with:
- email_log table tracking all outgoing emails with resend_id + delivery events
- inbound_emails table for Resend webhook-received messages
- Resend webhook handler (/webhooks/resend) updating delivery status in real-time
- send_email() returns resend_id (str|None) instead of bool; all 9 worker
  handlers pass email_type= for per-type filtering
- Admin UI: sent log with HTMX filters, email detail with API-enriched HTML
  preview, inbox with unread badges + reply, compose with branded wrapping,
  audience management with contact list/remove
- Sidebar Email section with unread badge via blueprint context processor

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,18 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 ## [Unreleased]
 
 ### Added
+- **Admin Email Hub** (`/admin/emails`) — full email management dashboard with:
+  sent log (filterable by type/event/search, HTMX partial updates), email detail
+  with Resend API enrichment for HTML preview, inbound inbox with unread badges
+  and inline reply, compose form with branded template wrapping, and Resend
+  audience management with contact list/remove
+- **Email delivery tracking** — `email_log` table records every outgoing email
+  with resend_id; Resend webhook handler (`/webhooks/resend`) updates delivery
+  events (delivered, bounced, opened, clicked, complained) in real-time;
+  `inbound_emails` table stores received messages with full body
+- **send_email() returns resend_id** — changed return type from `bool` to
+  `str | None` (backward-compatible: truthy string works like True); all 9
+  worker handlers now pass `email_type=` for per-type filtering in the log
 - **Playtomic full data extraction** — expanded venue bounding boxes from 4 regions
   (ES, UK, DE, FR) to 23 globally (Italy, Portugal, NL, BE, AT, CH, Nordics, Mexico,
   Argentina, Middle East, USA); PAGE_SIZE increased from 20 to 100; availability