email: per-mailbox captured/matched counts on Email Capture (v0.1.0:65)

/api/email/accounts now returns captured + matched per account (from the per-mailbox
sighting table email_account_messages joined to emails; emails dedupe globally so an
email seen by two mailboxes counts for each). Each mailbox card on the Email Capture
page shows "<N> captured · <M> matched" so per-user coverage is visible, not just the
aggregate. Verified in preview with two seeded mailboxes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/index.html

@@ -10197,6 +10197,7 @@
                                     <div key={a.id} className="kpi-card">
                                         <div className="kpi-label">{a.email_address}</div>
                                         <div className="kpi-value" style={{ fontSize: '15px' }}>{a.sync_status || 'pending'}{a.backfill_complete ? '' : ' · backfilling'}</div>
+                                        <div className="kpi-subtitle">{(a.captured ?? 0)} captured · {(a.matched ?? 0)} matched</div>
                                         <div className="kpi-subtitle">{a.last_synced_at ? `last ${formatDate(a.last_synced_at)}` : 'never synced'}{a.sync_error ? ` · ${a.sync_error}` : ''}</div>
                                     </div>
                                 ))}