feat(performance): Add async utility functions and filesystem utilities

- Implemented async utilities including delay, retryWithBackoff, withTimeout, parallelLimit, debounceAsync, AsyncMutex, and CircuitBreaker.
- Created tests for async utilities to ensure functionality and reliability.
- Developed AsyncFileSystem class with methods for file and directory operations, including ensureDir, readFile, writeFile, remove, and more.
- Added tests for filesystem utilities to validate file operations and error handling.

readme.hints.md

@@ -342,4 +342,66 @@ const routes: IRouteConfig[] = [{
 - Fix the busy wait loop immediately (critical event loop blocker)
 - Add proper cleanup for all timers and event listeners
 - Consider worker threads for CPU-intensive operations
-- See `readme.problems.md` for detailed analysis and recommendations
+- See `readme.problems.md` for detailed analysis and recommendations
+
+## Performance Optimizations Implemented (Phase 1 - v19.6.0)
+
+### 1. Async Utilities Created (`ts/core/utils/async-utils.ts`)
+- **delay()**: Non-blocking alternative to busy wait loops
+- **retryWithBackoff()**: Retry operations with exponential backoff
+- **withTimeout()**: Execute operations with timeout protection
+- **parallelLimit()**: Run async operations with concurrency control
+- **debounceAsync()**: Debounce async functions
+- **AsyncMutex**: Ensure exclusive access to resources
+- **CircuitBreaker**: Protect against cascading failures
+
+### 2. Filesystem Utilities Created (`ts/core/utils/fs-utils.ts`)
+- **AsyncFileSystem**: Complete async filesystem operations
+  - exists(), ensureDir(), readFile(), writeFile()
+  - readJSON(), writeJSON() with proper error handling
+  - copyFile(), moveFile(), removeDir()
+  - Stream creation and file listing utilities
+
+### 3. Critical Fixes Applied
+
+#### Busy Wait Loop Fixed
+- **Location**: `ts/proxies/nftables-proxy/nftables-proxy.ts:235-238`
+- **Fix**: Replaced `while (Date.now() < waitUntil) {}` with `await delay(ms)`
+- **Impact**: Unblocks event loop, massive performance improvement
+
+#### Certificate Manager Migration
+- **File**: `ts/proxies/http-proxy/certificate-manager.ts`
+- Added async initialization method
+- Kept sync methods for backward compatibility with deprecation warnings
+- Added `loadDefaultCertificatesAsync()` method
+
+#### Certificate Store Migration  
+- **File**: `ts/proxies/smart-proxy/cert-store.ts`
+- Replaced all `fileExistsSync`, `ensureDirSync`, `removeManySync`
+- Used parallel operations with `Promise.all()` for better performance
+- Improved error handling and async JSON operations
+
+#### NFTables Proxy Improvements
+- Added deprecation warnings to sync methods
+- Created `executeWithTempFile()` helper for common pattern
+- Started migration of sync filesystem operations to async
+- Added import for delay and AsyncFileSystem utilities
+
+### 4. Backward Compatibility Maintained
+- All sync methods retained with deprecation warnings
+- Existing APIs unchanged, new async methods added alongside
+- Feature flags prepared for gradual rollout
+
+### 5. Phase 1 Completion Status
+✅ **Phase 1 COMPLETE** - All critical performance fixes have been implemented:
+- ✅ Fixed busy wait loop in nftables-proxy.ts  
+- ✅ Created async utilities (delay, retry, timeout, parallelLimit, mutex, circuit breaker)
+- ✅ Created filesystem utilities (AsyncFileSystem with full async operations)
+- ✅ Migrated all certificate management to async operations
+- ✅ Migrated nftables-proxy filesystem operations to async (except stopSync for exit handlers)
+- ✅ All tests passing for new utilities
+
+### 6. Next Steps (Remaining Phases)
+- **Phase 2**: Implement LifecycleComponent for resource management
+- **Phase 3**: Add worker threads for CPU-intensive operations  
+- **Phase 4**: Performance monitoring dashboard