Phase 5: reply drafts — template/LLM draft, edit, SMTP send (AUD-71)

Implements Phase 5 of AGENTS.md §11 (FR-8, FR-15):

- Message detail pane (GET /partials/message) with body, recommended
  action, reply identity, template picker, editable draft, and history.
- internal/reply: OmniRoute (OpenAI-compatible) chat client and a
  template-based draft generator. All non-JEV models go through
  OmniRoute (§10).
- internal/mailops: SMTP send over smtp.gmail.com:587 with STARTTLS and
  the app password, forcing IPv4 (§9); FR-15 reply identity (send as the
  arrived-at X-Pm-Original-To address, else "Sam Rolfe"); threading via
  In-Reply-To/References; -check-smtp safe verification; and a
  [Gmail]/Sent Mail thread check.
- Migration v5 stores messages.message_id_header and drafts.sent_at;
  mailfetch parses Message-ID.
- Send is user-triggered only: CSRF + UI confirm + confirm=yes guard,
  no auto-send, duplicate-send refused. A sent reply files the original
  under Replied-to/<address> and logs every step (FR-13).
- Tests for reply, mailops SMTP/identity/thread check, store drafts and
  migration v5, and the server draft/edit/send guards.
- docs/phase5-replies.md, README, .env.example, docker-compose updated.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

internal/store/messages.go

@@ -14,9 +14,12 @@ import (
 
 // Message is one row of the messages table.
 type Message struct {
-	ID              int64
-	GmailID         string
-	ThreadID        string
+	ID       int64
+	GmailID  string
+	ThreadID string
+	// MessageIDHeader is the RFC822 Message-ID header (Phase 5, FR-8). A reply
+	// uses it for In-Reply-To and References so Gmail keeps the thread.
+	MessageIDHeader string
 	FromAddr        string
 	ToAddr          string
 	Subject         string
@@ -67,11 +70,12 @@ func ValidFolder(folder string) bool {
 func (s *Store) UpsertMessage(ctx context.Context, m *Message) (int64, error) {
 	const q = `
 INSERT INTO messages (
-    gmail_id, thread_id, from_addr, to_addr, subject, body_text,
+    gmail_id, thread_id, message_id_header, from_addr, to_addr, subject, body_text,
     source_address, date_sent, received_at, imap_uid, imap_uidvalidity
-) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
 ON CONFLICT (gmail_id) DO UPDATE SET
     thread_id         = excluded.thread_id,
+    message_id_header = excluded.message_id_header,
     from_addr         = excluded.from_addr,
     to_addr           = excluded.to_addr,
     subject           = excluded.subject,
@@ -88,6 +92,7 @@ ON CONFLICT (gmail_id) DO UPDATE SET
 	_, err := s.db.ExecContext(ctx, q,
 		m.GmailID,
 		nullString(m.ThreadID),
+		nullString(m.MessageIDHeader),
 		nullString(m.FromAddr),
 		nullString(m.ToAddr),
 		nullString(m.Subject),
@@ -110,6 +115,35 @@ ON CONFLICT (gmail_id) DO UPDATE SET
 	return id, nil
 }
 
+// MessageByID loads one message including the reply fields (body, source
+// address, and Message-ID header). It is the read path for a reply draft.
+func (s *Store) MessageByID(ctx context.Context, id int64) (Message, error) {
+	const q = `
+SELECT m.id, m.gmail_id, COALESCE(m.thread_id, ''), COALESCE(m.from_addr, ''),
+       COALESCE(m.to_addr, ''), COALESCE(m.subject, ''), COALESCE(m.body_text, ''),
+       COALESCE(m.source_address, ''), COALESCE(m.date_sent, ''), m.received_at,
+       COALESCE(m.imap_uid, 0), COALESCE(m.imap_uidvalidity, 0),
+       COALESCE(m.folder, 'inbox'), COALESCE(m.mailbox, 'INBOX'),
+       COALESCE(m.message_id_header, '')
+FROM messages m WHERE m.id = ?`
+	var (
+		m        Message
+		dateSent string
+		received string
+	)
+	err := s.db.QueryRowContext(ctx, q, id).Scan(
+		&m.ID, &m.GmailID, &m.ThreadID, &m.FromAddr, &m.ToAddr, &m.Subject,
+		&m.BodyText, &m.SourceAddress, &dateSent, &received,
+		&m.IMAPUID, &m.IMAPUIDValidity, &m.Folder, &m.Mailbox, &m.MessageIDHeader,
+	)
+	if err != nil {
+		return Message{}, fmt.Errorf("load message %d: %w", id, err)
+	}
+	m.DateSent = parseSQLTime(dateSent)
+	m.ReceivedAt = parseSQLTime(received)
+	return m, nil
+}
+
 // ListMessages returns the most recent messages, newest first, joined to their
 // latest classification when one exists.
 func (s *Store) ListMessages(ctx context.Context, limit int) ([]MessageListItem, error) {