In-site feedback reply (plain-text v1)

Reply to a reader from the admin inbox instead of a mailto. Per Codex: keep v1
plain text (no rich editor — defers the user's bold/bullets ask as a fast-follow).

* DB: feedback_replies table (feedback_id, user_id, message, sent_to, sent_at),
  created on the live DB.
* email_send.send_feedback_reply: plain-text "Re: Your Upbeat Bytes feedback"
  with a quoted context block, no analytics/account details.
* API: POST /api/admin/feedback/{id}/reply — admin-gated, requires the feedback
  exists (404) and has a contact_email (400), trims+caps the message; sends via
  SMTP and only records the reply on success (502 on send failure so the UI keeps
  the draft); marks the item read. Feedback list now includes each item's replies.
* Frontend: inline composer (Send/Cancel, sending state, error keeps draft) +
  reply thread under the message; Reply only shows when there's an address,
  else "No reply address".

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

goodnews/email_send.py

@@ -63,6 +63,21 @@ def send_feedback(to: str, category: str, message: str, contact: str | None, who
     send_email(to, subject, text)
 
 
+def send_feedback_reply(to: str, reply_message: str, original_message: str) -> None:
+    """Reply to a reader's feedback from the admin inbox (plain text). Quotes
+    their original note for context; exposes no analytics/account details."""
+    subject = "Re: Your Upbeat Bytes feedback"
+    quoted = "\n".join("> " + line for line in (original_message or "").splitlines())
+    text = (
+        f"{reply_message}\n\n"
+        "—\n"
+        "In reply to your note to Upbeat Bytes:\n"
+        f"{quoted}\n\n"
+        "Thanks for reaching out.\n— Upbeat Bytes\n"
+    )
+    send_email(to, subject, text)
+
+
 def send_magic_link(to: str, link: str) -> None:
     """Send a calm, single-purpose sign-in email."""
     subject = "Your Upbeat Bytes sign-in link"