feat(admin): app-log preview surfaces last 1h of structured events with filter + JSON inspector

Wires the in-memory ring buffer (`src/lib/logging/in-memory-buffer.ts`)
into `transports.emitEvent()` so every wide event that survives the
sampler also lands in a 500-entry per-process buffer. Adds the
`app-logs` admin section slug, the renderer case, and the route entry
exports needed for the new section component to mount.

The buffer is volatile and per-process — a worker-only event won't
show up in the web buffer, and a restart drops everything. The section
header copy spells that out so admins know to keep Loki configured for
durable diagnostics. Egress through `/api/admin/app-logs` runs every
event through `redactSecrets()` so a stray Bearer / hlk_ / sk- token
in an `error.message` never leaks to the admin UI; storage stays raw
to keep the diagnostic value when shipped to Loki.

The companion buffer + transports tests live under
`src/lib/logging/__tests__/in-memory-buffer.test.ts` and
`transports-buffer.test.ts` (committed separately as part of the
buffer scaffolding). The route-level tests in
`src/app/api/admin/app-logs/__tests__/route.test.ts` cover newest-
first ordering, traceId / level / action filters, the `limit` cap,
secret redaction on egress, and the Zod-rejected invalid `level` case.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/admin/[section]/renderer.tsx

@@ -17,6 +17,7 @@ import type { JSX } from "react";
 import { useAuth } from "@/hooks/use-auth";
 import { useTranslations } from "@/lib/i18n/context";
 import { ApiTokenOverviewSection } from "@/components/admin/api-token-overview-section";
+import { AppLogPreviewSection } from "@/components/admin/app-log-preview-section";
 import { BackupsSection } from "@/components/admin/backups-section";
 import { DangerZoneSection } from "@/components/admin/danger-zone-section";
 import { FeedbackInboxSection } from "@/components/admin/feedback-inbox-section";
@@ -127,6 +128,15 @@ export function AdminSectionRenderer({
           <LoginOverviewSection />
         </SectionFrame>
       );
+    case "app-logs":
+      return (
+        <SectionFrame
+          title={t("admin.section.app-logs.title")}
+          subtitle={t("admin.section.app-logs.subtitle")}
+        >
+          <AppLogPreviewSection />
+        </SectionFrame>
+      );
     case "backups":
       return (
         <SectionFrame