[clbotdev]

Implements the new Send a test email design for broadcasts and the sequence email editor.

• Send to: address chips with a remove button and an "N of 5" counter. Enter, comma, space or paste adds addresses; Backspace removes the last one; duplicates are skipped.
• Summary card: From (the delivery source's sender), Via (source name plus "✓ Same as the real email"), and Subject with a [Test] tag. The callers now pass the subject.
• Mailing address: the dialog checks general settings when it opens. If the address is missing, an amber prompt explains why it's needed and lets you add it inline with Add mailing address. Send stays disabled until then, and the footer says "Add your mailing address to send". If the API reports a missing address, the same prompt appears.
• Footer: separated by a rule, shows the last test time on the left and Cancel / Send test on the right.

Tests

• New send-test-dialog.test.tsx: recipient parsing, chips and counter, the summary rows, and saving the mailing address inline. All web tests pass (93), along with lint and typecheck.
• Browser E2E on a scratch stack: no address → prompt shown and Send disabled → address saved inline → second chip added → test delivered via Mailpit QA. The sequence editor dialog shows no prompt once the address is saved.