perf: bound SWR cache, clean stale storage, cap annotations

Add LRU cache provider (200 entries) to prevent unbounded SWR memory
growth. Clean up stale PKCE localStorage keys on app init. Cap chart
annotations to 20 visible reference lines with overflow indicator.

lib/auth/context.tsx

@@ -7,6 +7,7 @@ import { LoadingOverlay, useSessionSync, SessionExpiryWarning } from '@ciphera-n
 import { logoutAction, getSessionAction, setSessionAction } from '@/app/actions/auth'
 import { getUserOrganizations, switchContext } from '@/lib/api/organization'
 import { logger } from '@/lib/utils/logger'
+import { cleanupStaleStorage } from '@/lib/utils/storage-cleanup'
 
 interface User {
   id: string
@@ -131,6 +132,8 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
   // Initial load
   useEffect(() => {
     const init = async () => {
+        cleanupStaleStorage()
+
         // * 1. Check server-side session (cookies)
         let session: Awaited<ReturnType<typeof getSessionAction>> = null
         try {