fix(build): keep the server logger out of client bundles

The production webpack build failed with UnhandledSchemeError: client
components imported @/lib/logger, which binds pino, AsyncLocalStorage
(node:async_hooks), node:crypto and node:fs — and validates server env on
import. The UI fixture aliased those modules, so the harness and tests
never hit it.

- add src/lib/browser-log.ts: browser-safe logger with the same interface;
  errors are forwarded to /api/diagnostics/errors via reportBrowserError
- guard src/lib/logger.ts with server-only and drop its now-dead browser
  branches
- switch the 11 client components/hooks to @/lib/browser-log

Verified with the Dockerfile's production build (pnpm run build) and the
full vitest suite.

src/components/admin/media-grid.tsx

@@ -4,8 +4,8 @@ import { useTranslations } from "next-intl";
 import { useCallback, useEffect, useMemo, useRef, useState } from "react";
 import { deleteMedia, uploadMedia } from "@/actions/admin-media";
 import { useConfirmDialog } from "@/components/admin/confirm-dialog";
+import { logger } from "@/lib/browser-log";
 import { formatDate } from "@/lib/format-date";
-import { logger } from "@/lib/logger";
 import type { MediaFile } from "@/lib/media-files";
 import { loadMediaFiles, validImageUrl } from "@/lib/media-files";