add more status updates

apps/submissions/emails.py

@@ -1,6 +1,6 @@
 """Outgoing email -- plan.md §7 (state-transition side effects).
 
-Three public functions, one per dedicated template:
+Five public functions, one per dedicated template:
 
   send_confirmation_email(submission)
       Guest path: token-link emailed immediately after `SubmitView` creates
@@ -20,7 +20,19 @@ Three public functions, one per dedicated template:
       rejection reason in the email as on the public detail page.
       Template: `emails/rejected.*`.
 
-All three delegate to Django's email machinery. The backend is wired in
+  send_printing_email(submission)
+      Fired on any transition into `status = printing` (operator clicks
+      "Start printing" in admin). Excited tone: "your print is on the
+      bed right now". Template: `emails/printing.*`.
+
+  send_completed_email(submission)
+      Fired on any transition into `status = completed` (operator clicks
+      "Mark completed"). Pickup-ready announcement; renders
+      `submission.operator_notes` as a "note from the operator" callout
+      when present (typically pickup instructions). Template:
+      `emails/completed.*`.
+
+All five delegate to Django's email machinery. The backend is wired in
 `hamprint/settings/base.py`: Mailtrap via `django-anymail` when
 `MAILTRAP_API_TOKEN` is present, console when not. Send failures are caught
 + logged so a flaky transport never blocks the submission flow.
@@ -146,3 +158,20 @@ def send_verifying_email(sub: Submission) -> bool:
     will be the queued / printing one."""
     detail_url = f"{settings.SITE_URL}/p/{sub.slug}/"
     return _send("verifying", sub, {"detail_url": detail_url})
+
+
+def send_printing_email(sub: Submission) -> bool:
+    """Notify the submitter that the print has just started (plan.md §7.3
+    `queued -> printing` transition). Excited tone -- the operator just
+    clicked "Start printing" in admin and the first layer is going down."""
+    detail_url = f"{settings.SITE_URL}/p/{sub.slug}/"
+    return _send("printing", sub, {"detail_url": detail_url})
+
+
+def send_completed_email(sub: Submission) -> bool:
+    """Notify the submitter that the print finished successfully and is
+    ready for pickup (plan.md §7.3 `printing -> completed` transition).
+    `submission.operator_notes` is rendered when present so any
+    pickup-instruction the operator typed in admin reaches the user."""
+    detail_url = f"{settings.SITE_URL}/p/{sub.slug}/"
+    return _send("completed", sub, {"detail_url": detail_url})