feat: implement clean embedding architecture with Q8/FP32 precision control

- Unified embedding system with single EmbeddingManager
- Q8 model support with 75% smaller footprint (23MB vs 90MB)
- Intelligent precision auto-selection based on environment
- Clean cached embeddings with TTL and memory management
- Zero-config setup with smart defaults
- Complete storage structure documentation
- Removed legacy worker and hybrid managers
- Streamlined model configuration and precision management

src/config/index.ts

@@ -13,6 +13,15 @@ export {
   logModelConfig
 } from './modelAutoConfig.js'
 
+// Model precision manager
+export {
+  ModelPrecisionManager,
+  getModelPrecision,
+  setModelPrecision,
+  lockModelPrecision,
+  validateModelPrecision
+} from './modelPrecisionManager.js'
+
 // Storage configuration
 export { 
   autoDetectStorage,