feat: persist pinned libraries per user with cross-device sync (#20)

Store pinned library IDs on the user record and expose GET/PUT
/me/pinned-libraries endpoints. The web client now loads and saves pins
through the API, migrates legacy localStorage data once, and applies
pinned ordering on both the libraries and home pages.

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: truewhile <truewhile@users.noreply.github.com>

web/src/utils/pinnedLibraries.ts

@@ -1,4 +1,7 @@
+import { profileAPI } from '../api/profile'
+
 const STORAGE_KEY = 'mebox_pinned_libraries'
+const MIGRATION_KEY = 'mebox_pinned_libraries_migrated'
 
 function parsePinnedIds(raw: string | null): string[] {
   if (!raw) return []
@@ -11,28 +14,74 @@ function parsePinnedIds(raw: string | null): string[] {
   }
 }
 
-export function readPinnedLibraryIds(): string[] {
+export function readLegacyPinnedLibraryIds(): string[] {
   if (typeof window === 'undefined') return []
   return parsePinnedIds(window.localStorage.getItem(STORAGE_KEY))
 }
 
-export function writePinnedLibraryIds(ids: string[]): void {
+function writeLegacyPinnedLibraryIds(ids: string[]): void {
   if (typeof window === 'undefined') return
+  if (ids.length === 0) {
+    window.localStorage.removeItem(STORAGE_KEY)
+    return
+  }
   window.localStorage.setItem(STORAGE_KEY, JSON.stringify(ids))
 }
 
-export function togglePinnedLibraryId(id: string): string[] {
-  const current = readPinnedLibraryIds()
+function markPinnedLibrariesMigrated(): void {
+  if (typeof window === 'undefined') return
+  window.localStorage.setItem(MIGRATION_KEY, '1')
+  window.localStorage.removeItem(STORAGE_KEY)
+}
+
+function hasPinnedLibrariesMigrated(): boolean {
+  if (typeof window === 'undefined') return true
+  return window.localStorage.getItem(MIGRATION_KEY) === '1'
+}
+
+export async function loadPinnedLibraryIds(): Promise<string[]> {
+  const remote = await profileAPI.getPinnedLibraries()
+  if (!hasPinnedLibrariesMigrated()) {
+    const legacy = readLegacyPinnedLibraryIds()
+    if (legacy.length > 0 && remote.length === 0) {
+      const migrated = await profileAPI.setPinnedLibraries(legacy)
+      markPinnedLibrariesMigrated()
+      return migrated
+    }
+    markPinnedLibrariesMigrated()
+  }
+  return remote
+}
+
+export async function savePinnedLibraryIds(ids: string[]): Promise<string[]> {
+  const saved = await profileAPI.setPinnedLibraries(ids)
+  writeLegacyPinnedLibraryIds(saved)
+  return saved
+}
+
+export function togglePinnedLibraryId(current: string[], id: string): string[] {
   const index = current.indexOf(id)
-  const next = index >= 0 ? current.filter((item) => item !== id) : [...current, id]
-  writePinnedLibraryIds(next)
-  return next
+  return index >= 0 ? current.filter((item) => item !== id) : [...current, id]
 }
 
 export function isLibraryPinned(id: string, pinnedIds: string[]): boolean {
   return pinnedIds.includes(id)
 }
 
+export function sortByPinnedIds<T extends { id: string }>(items: T[], pinnedIds: string[]): T[] {
+  if (pinnedIds.length === 0) return items
+  const rank = new Map(pinnedIds.map((pinnedId, index) => [pinnedId, index]))
+  return [...items].sort((a, b) => {
+    const aRank = rank.get(a.id)
+    const bRank = rank.get(b.id)
+    const aPinned = aRank !== undefined
+    const bPinned = bRank !== undefined
+    if (aPinned !== bPinned) return aPinned ? -1 : 1
+    if (aPinned && bPinned) return aRank - bRank
+    return 0
+  })
+}
+
 export function sortLibraryPreviews<T extends { library: { id: string } }>(items: T[], pinnedIds: string[]): T[] {
   if (pinnedIds.length === 0) return items
   const rank = new Map(pinnedIds.map((id, index) => [id, index]))