feat: remove legacy ImportManager, standardize getStats() API

- Removed ImportManager class and exports (use brain.import() instead)
- Fixed all documentation: getStatistics() → getStats()
- Updated 41 files across codebase for consistency
- Removed ImportManager section from API docs
- Added v3.30.0 migration guide to CHANGELOG

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

examples/tests/test-real-ai.js

@@ -68,7 +68,7 @@ async function testAllFeatures() {
     console.log(`   ✅ Found ${tripleResults.length} results with Triple Intelligence`)
     
     console.log('\n7. Testing statistics and health...')
-    const stats = await brain.getStatistics()
+    const stats = brain.getStats()
     console.log(`   ✅ Total items: ${stats.totalItems}`)
     console.log(`   ✅ Dimensions: ${stats.dimensions}`)
     console.log(`   ✅ Index size: ${stats.indexSize}`)