feat: PWA manifest + the Ghost Log (Workstream C)

manifest.webmanifest referencing the icon assets that actually exist
(sizes verified with file, not asserted), standalone display, no service
worker — offline séance is meaningless and SW cache bugs are not worth it.

GET /api/seances/recent: last 12 sessions in exactly three queries
(sessions+entity join, one GROUP BY for counts, one window-function query
for up to 3 echoes per session). Echoes filter on utterance payload kinds
because DB event kinds carry no greeting/manifest — the agent verified
where _speak actually writes rather than trusting the spec's phrasing.

/log page: entity glyphs, relative in-fiction timestamps, counts, echo
lines in transcript style, gated like the séance, 390px-safe.

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

frontend/src/pages/SeancePage.tsx

@@ -269,6 +269,10 @@ function SeanceSession({ username }: { username: string }) {
             {t('nav.codex')}
           </Link>
 
+          <Link to="/log" className="seance-codex-link">
+            {t('nav.log', { defaultValue: 'log' })}
+          </Link>
+
           <Link to="/inventory" className="seance-codex-link">
             {t('nav.inventory', { defaultValue: 'inventory' })}
           </Link>