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>

PROJECT.md

@@ -1,7 +1,7 @@
 # Padelnomics — Project Tracker
 
 > Move tasks across columns as you work. Add new tasks at the top of the relevant column.
-> Last updated: 2026-02-22.
+> Last updated: 2026-02-23.
 
 ---
 
@@ -100,6 +100,7 @@
 - [x] Comprehensive admin: users, tasks, leads, suppliers, CMS templates, scenarios, articles, feedback
 - [x] Task queue management (list, retry, delete)
 - [x] Lead funnel stats on admin dashboard
+- [x] Email hub (`/admin/emails`) — sent log, inbox, compose, audiences, delivery event tracking via Resend webhooks
 
 ### SEO & Legal
 - [x] Sitemap (both language variants, `<lastmod>` on all entries)
@@ -193,7 +194,7 @@ _Move here when you start working on it._
 ### Bugs / Tech Debt
 - [ ] Resend audiences: two segments both using "waitlist-auth" — review audience/segment model and fix duplication
 - [ ] Transactional emails not all translated to German — some emails still sent in English regardless of user language
-- [ ] Resend inbound emails enabled — plan how to integrate (webhook routing, reply handling, support inbox?)
+- [x] ~~Resend inbound emails enabled~~ — integrated: webhook handler + admin inbox with reply (done in email hub)
 - [ ] Extraction: Playtomic API only returns ~20 venues per bbox — investigate smaller/targeted bboxes
 
 ### Marketing & Content