Fix SMTP delivery, add password reset and user deletion

SMTP:
- Add connection/greeting/socket timeouts so a stalled Gmail
  connection no longer hangs sign-up
- Wrap sendMail in try/catch and fall back to logging the code
- Derive secure from port (465 implicit TLS vs 587 STARTTLS)
- Strip whitespace from the Gmail app password
- Document SMTP_HOST/SMTP_PORT in .env.example and environment.d.ts

Password reset (new):
- POST /(api)/auth/forgot-password emails a 6-digit code and does
  not reveal whether the address is registered
- POST /(api)/auth/reset-password validates the code, sets the new
  password, verifies the email, and signs the user in
- password_reset_codes table added to seed-db.mjs
- "Forgot password?" flow on the mobile sign-in screen

User deletion (new):
- DELETE /(api)/admin/users/[id], owner-only, blocks self-deletion
- Delete button with confirmation on the dashboard Users page

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

dashboard/src/index.css

@@ -176,6 +176,25 @@ select {
   margin: 10px 0;
 }
 
+.muted {
+  color: var(--muted);
+  font-size: 13px;
+}
+
+.card .sub {
+  color: var(--muted);
+  font-size: 12px;
+  margin-top: 4px;
+}
+
+.card.warn .value {
+  color: var(--danger);
+}
+
+.pager {
+  margin-top: 14px;
+}
+
 .login-wrap {
   margin: auto;
   width: 340px;