Show per-member token usage badges on panel bubbles

memberUsage was already populated for CLI members (from the result event)
and Anthropic-API members (via the tool loop), but it was never written to
the panel_member_done SSE event or the persisted content JSON, so the
frontend had no token data to render.

Add the token fields (input/output/cacheRead/cacheCreation) to both the
SSE event and the persisted JSON, and render them via a shared
buildPanelMemberMeta helper used by both the live stream and history, so
the badge survives F5. OpenAI members (no per-turn tokens), error members,
and pre-existing history without token fields fall through to no badge.

The badge is display-only; aggregation into the worker/chain total via
seedUsage is unchanged, so there is no double counting and no DB migration.

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

wwwroot/css/chat.css

@@ -1237,6 +1237,17 @@
   border-color: var(--accent, #9b6dff);
 }
 
+/* Per-Member Token-Badge am unteren Rand der Panel-Bubble (live + History) */
+.panel-member-meta {
+  display: flex;
+  flex-wrap: wrap;
+  justify-content: flex-end;
+  gap: var(--badge-spacing);
+  margin-top: var(--badge-spacing);
+  font-size: var(--font-size);
+  opacity: var(--semi-transparent);
+}
+
 /* MoA: Trenner zwischen Proposer-Runden */
 .panel-layer-divider {
   display: flex;