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>

src/index.ts

@@ -70,9 +70,7 @@ export type {
   NeuralImportOptions
 } from './cortex/neuralImport.js'
 
-// Export Import Manager (comprehensive data import)
-export { ImportManager, createImportManager } from './importManager.js'
-export type { ImportOptions, ImportResult } from './importManager.js'
+// Import Manager removed - use brain.import() instead (available on all Brainy instances)
 
 // Augmentation types are already exported later in the file