chore(PBI-76): remove unused readLocalStoragePref helper

No consumers left after migrating sprint-backlog, pbi-list,
story-panel, jobs-column, and debug-store to user-settings.

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

lib/use-local-storage-pref.ts

@@ -1,22 +0,0 @@
-/**
- * SSR-safe synchronous read of a localStorage value with a typed parser.
- *
- * Use inside `useState(() => readLocalStoragePref(...))` so the first render
- * already has the persisted value — no useEffect-driven re-render flicker.
- *
- * On the server `window` is undefined → returns `fallback`. On the client the
- * raw value is parsed; if the parser returns `null` the fallback is used.
- * Hydration mismatches between server-rendered HTML (default) and the
- * client-rendered tree (persisted) are accepted: React adapts the DOM in the
- * same hydration pass without a visible flicker for matching values.
- */
-export function readLocalStoragePref<T>(
-  key: string,
-  parse: (raw: string) => T | null,
-  fallback: T,
-): T {
-  if (typeof window === 'undefined') return fallback
-  const raw = window.localStorage.getItem(key)
-  if (raw === null) return fallback
-  return parse(raw) ?? fallback
-}