feat: make the Ghost Log actually do something

It was read-only: one link on the whole page ("back to séance"), no way
to get from "I talked to this spirit" to anything about them. Fixed with
three additions, all client-side against data already fetched in one
call — no backend change:

- Every entity glyph and name links straight to its Codex page.
- Echoes past the first are collapsed behind a "+N more" toggle instead
  of always showing up to 3 — a card reads cleanly at a glance, with
  detail one tap away.
- A channel filter (only shown once >1 mode is actually present in the
  log) so a seeker with a long history can find "just the radio nights."

Deliberately did NOT add a "revisit this spirit" button. Contact is a
probabilistic channel draw (RETURN_CHANCE), not "resume this entity" —
a button that just navigated to /seance would be indistinguishable from
the existing back link and would imply a guarantee the app doesn't make.
Cosmetic interactivity isn't worth shipping.

6 new tests. 372 frontend tests pass total; i18n parity holds.

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

frontend/src/i18n/en.json

@@ -28,6 +28,11 @@
     "error": "the log will not open — the veil resists tonight",
     "empty": "no séances yet — the log waits",
     "noEntity": "no one answered",
+    "filterLabel": "filter by channel",
+    "filterAll": "all channels",
+    "showMore_one": "+{{count}} more echo",
+    "showMore_other": "+{{count}} more echoes",
+    "showLess": "show less",
     "counts": {
       "question_one": "{{count}} question",
       "question_other": "{{count}} questions",