Add queued email notifications for collaboration events

.project/milestones/milestone-04-collaboration.md

@@ -7,12 +7,12 @@
 
 ### Week 7: Comments & Notifications
 
-- [x] Comment system (backend complete, UI partial)
+- [x] Comment system (backend + UI wired)
   - [x] Comment creation endpoint (web)
   - [x] Comment threading (parent/child) - schema supports it
   - [x] Line/section anchoring (hash-based)
   - [x] Comment resolution (mark as resolved)
-  - [ ] Comment display in the Go-served browser UI (JS exists but needs wiring)
+  - [x] Comment display in the Go-served browser UI (`c39c50b` dropdown menu + comment side panel, `comments.js` +330 lines)
    
 - [x] Notification system (backend complete)
   - [x] Notification queue in database
@@ -29,18 +29,18 @@
 
 ### Week 8: Email Integration & Conflict Resolution
 
-- [ ] Postmark integration
+- [x] Postmark integration
   - [x] SMTP sender stub (NoOp + SMTP implementations)
-  - [ ] Postmark adapter
-  - [ ] Plain-text email templates
-  - [ ] Outgoing email queue with retry
+  - [x] Postmark adapter (`email/postmark.go`)
+  - [x] Plain-text email templates (`email/templates.go`)
+  - [x] Outgoing email queue with retry (`email/queue.go` + migration 000016)
   - [ ] Webhook endpoint for inbound email
-   
-- [ ] Email notification types
-  - [ ] File changed notification
-  - [ ] New comment notification
-  - [ ] Mention notification (@username)
-  - [ ] Conflict alert notification
+    
+- [x] Email notification types
+  - [x] File changed notification
+  - [x] New comment notification
+  - [ ] Mention notification (@username) — template exists, mention detection not wired
+  - [ ] Conflict alert notification — template exists, not triggered from sync flow
   - [ ] Digest summary email
    
 - [ ] Email reply handling
@@ -62,7 +62,7 @@
 - [x] Comments are linked to document version (hash)
 - [x] Comment threading works (reply to reply) (schema supports it)
 - [x] Users can watch files or folders for changes (API exists)
-- [ ] Email notifications sent within 1 minute of event (NoOp sender currently)
+- [x] Email notifications sent within 1 minute of event (Postmark adapter + queue with retry)
 - [ ] Replying to notification email creates a comment
 - [ ] Digest emails batch notifications by time window
 - [x] Conflicts display side-by-side diff (M2 sync)
@@ -70,11 +70,11 @@
 - [ ] Resolved comments are hidden but accessible in history
 
 ### Non-Functional
-- [ ] Emails are plain-text only (no HTML)
+- [x] Emails are plain-text only (no HTML) — enforced by templates, verified by test
 - [ ] Email threading works in Gmail, Outlook, Apple Mail
 - [ ] Webhook signature verified for inbound email
-- [ ] Failed emails retried 3 times with exponential backoff
-- [ ] Email queue doesn't block web requests (async processing)
+- [x] Failed emails retried 3 times with exponential backoff — queue.go, verified by test
+- [x] Email queue doesn't block web requests (async processing) — worker runs in goroutine
 
 ### Email Template Examples