User feedback + expanded privacy-respecting admin stats

Feedback:
- feedback table; POST /api/feedback (anonymous-ok, optional category/email,
  honeypot + per-day flood cap) stores + emails the admin; GET /api/admin/feedback.
- Shared feedback store + FeedbackModal; a speech-bubble opens it from the desktop
  header, the mobile top bar (logo moves left), the footer, and /account. Feedback
  section in /admin.

Stats (additive, same privacy model — no IP/UA/referrer/raw terms):
- Event vocab: summary_viewed (fired on /a load), full_story (card → source),
  not_today/less_like_this/hide_topic, replace_used/replace_none, paywall_replace,
  paywalled_source_open. Card title/image opens /a (no double-count); history
  records via keepalive so it survives the nav.
- Dashboard: Accounts card (counts only), reading funnel (summary→source rate),
  emotional-mix & friction, paywall, returning-visitor buckets. (Health metrics
  deferred to a future monitoring dashboard.) 131 tests pass.

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

goodnews/email_send.py

@@ -50,6 +50,19 @@ def send_email(to: str, subject: str, text: str, html: str | None = None) -> Non
         server.send_message(msg)
 
 
+def send_feedback(to: str, category: str, message: str, contact: str | None, who: str) -> None:
+    """Notify the admin of new user feedback (plain text is plenty here)."""
+    subject = f"Upbeat Bytes feedback · {category}"
+    reply = contact or "(none given)"
+    text = (
+        f"New feedback ({category})\n"
+        f"From: {who}\n"
+        f"Reply to: {reply}\n\n"
+        f"{message}\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"