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/store.go

@@ -144,6 +144,21 @@ func (s *Store) applyMigrations(ctx context.Context) error {
 			return fmt.Errorf("record schema version 4: %w", err)
 		}
 	}
+	if version < 5 {
+		// Phase 5 (FR-8): store the RFC822 Message-ID so a reply can set
+		// In-Reply-To/References and stay in the same Gmail thread, and record
+		// when a draft was sent.
+		if err := s.ensureColumn(ctx, "messages", "message_id_header", "TEXT"); err != nil {
+			return err
+		}
+		if err := s.ensureColumn(ctx, "drafts", "sent_at", "TEXT"); err != nil {
+			return err
+		}
+		if _, err := s.db.ExecContext(ctx,
+			`INSERT OR IGNORE INTO schema_migrations (version) VALUES (5)`); err != nil {
+			return fmt.Errorf("record schema version 5: %w", err)
+		}
+	}
 	return nil
 }