Add Cloudflare email and collaboration workflows

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

@@ -9,9 +9,9 @@
 
 - [x] Comment system (backend + UI wired)
   - [x] Comment creation endpoint (web)
-  - [x] Comment threading (parent/child) - schema supports it
+  - [x] Comment threading (parent/child) with nested browser replies
   - [x] Line/section anchoring (hash-based)
-  - [x] Comment resolution (mark as resolved)
+  - [x] Whole-thread resolution with resolved-history view
   - [x] Comment display in the Go-served browser UI (`c39c50b` dropdown menu + comment side panel, `comments.js` +330 lines)
    
 - [x] Notification system (backend complete)
@@ -21,10 +21,10 @@
   - [ ] Global notification settings
   - [ ] Digest mode (hourly/daily batches)
    
-- [x] Web notification UI (backend complete, JS partial)
-  - [x] Notification bell with unread count - API exists
-  - [x] Notification list dropdown - API exists
-  - [x] Mark as read functionality - API exists
+- [x] Web notification UI
+  - [x] Notification bell with unread count
+  - [x] Notification list dropdown
+  - [x] Mark one/all as read functionality
   - [ ] Notification preferences page
 
 ### Week 8: Email Integration & Conflict Resolution
@@ -34,6 +34,7 @@
   - [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)
+  - [x] Cloudflare Email Service REST adapter (`email/cloudflare.go`)
   - [ ] Webhook endpoint for inbound email
     
 - [x] Email notification types
@@ -60,20 +61,20 @@
 ### Functional
 - [x] Users can add comments to specific lines in a document (API exists)
 - [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)
-- [x] Email notifications sent within 1 minute of event (Postmark adapter + queue with retry)
+- [x] Comment threading works (reply to reply) in the browser and API
+- [x] Users can watch files or folders for changes (document UI + APIs)
+- [x] Email notifications queued within 1 minute of event (Postmark, Cloudflare, or SMTP sender)
 - [ ] Replying to notification email creates a comment
 - [ ] Digest emails batch notifications by time window
-- [x] Conflicts display side-by-side diff (M2 sync)
+- [x] Conflicts display a unified diff (M2 sync)
 - [x] Users can resolve conflicts via web UI (M2 sync)
-- [ ] Resolved comments are hidden but accessible in history
+- [x] Resolved comments are hidden but accessible in history
 
 ### Non-Functional
 - [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
-- [x] Failed emails retried 3 times with exponential backoff — queue.go, verified by test
+- [x] Temporary email failures retried 3 times with exponential backoff; permanent provider rejections fail immediately
 - [x] Email queue doesn't block web requests (async processing) — worker runs in goroutine
 
 ### Email Template Examples
@@ -166,7 +167,7 @@ CREATE TABLE watchers (
 
 - [ ] All acceptance criteria pass
 - [ ] Email flows tested with real Postmark account
-- [ ] Comment threading tested with 3+ levels
+- [x] Comment threading tested with 3+ levels
 - [ ] Conflict resolution tested with 2+ concurrent editors
 - [ ] Notification preferences persist across sessions
 - [ ] Digest mode tested with 24-hour window