feat: create highlight sync manager with queue logic

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Co-Authored-By: Claude <noreply@anthropic.com>

__tests__/lib/highlight-sync-manager.test.ts

@@ -0,0 +1,79 @@
+import { HighlightSyncManager } from '@/lib/highlight-sync-manager'
+import { BibleHighlight } from '@/types'
+
+describe('HighlightSyncManager', () => {
+  let manager: HighlightSyncManager
+
+  beforeEach(() => {
+    manager = new HighlightSyncManager()
+  })
+
+  it('should add highlight to sync queue', async () => {
+    const highlight: BibleHighlight = {
+      id: 'h-1',
+      verseId: 'v-1',
+      color: 'yellow',
+      createdAt: Date.now(),
+      updatedAt: Date.now(),
+      syncStatus: 'pending'
+    }
+
+    await manager.queueHighlight(highlight)
+    const pending = await manager.getPendingSyncItems()
+
+    expect(pending.length).toBe(1)
+    expect(pending[0].id).toBe('h-1')
+  })
+
+  it('should mark highlight as syncing', async () => {
+    const highlight: BibleHighlight = {
+      id: 'h-1',
+      verseId: 'v-1',
+      color: 'yellow',
+      createdAt: Date.now(),
+      updatedAt: Date.now(),
+      syncStatus: 'pending'
+    }
+
+    await manager.queueHighlight(highlight)
+    await manager.markSyncing(['h-1'])
+
+    const syncing = await manager.getSyncingItems()
+    expect(syncing.length).toBe(1)
+  })
+
+  it('should mark highlight as synced', async () => {
+    const highlight: BibleHighlight = {
+      id: 'h-1',
+      verseId: 'v-1',
+      color: 'yellow',
+      createdAt: Date.now(),
+      updatedAt: Date.now(),
+      syncStatus: 'pending'
+    }
+
+    await manager.queueHighlight(highlight)
+    await manager.markSynced(['h-1'])
+
+    const pending = await manager.getPendingSyncItems()
+    expect(pending.length).toBe(0)
+  })
+
+  it('should retry sync on error', async () => {
+    const highlight: BibleHighlight = {
+      id: 'h-1',
+      verseId: 'v-1',
+      color: 'yellow',
+      createdAt: Date.now(),
+      updatedAt: Date.now(),
+      syncStatus: 'pending'
+    }
+
+    await manager.queueHighlight(highlight)
+    await manager.markError(['h-1'], 'Network error')
+    await manager.markSyncing(['h-1'])
+
+    const syncing = await manager.getSyncingItems()
+    expect(syncing.length).toBe(1)
+  })
+})