added new di with connection pool and rebuild of the database/cache services

libs/mongodb-client/src/index.ts

@@ -20,6 +20,9 @@ export type {
   RawDocument,
   SecFiling,
   SentimentData,
+  PoolMetrics,
+  ConnectionEvents,
+  DynamicPoolConfig,
 } from './types';
 
 // Factory functions
@@ -28,10 +31,4 @@ export {
   createAndConnectMongoDBClient,
 } from './factory';
 
-// Singleton instance
-export {
-  getMongoDBClient,
-  connectMongoDB,
-  getDatabase,
-  disconnectMongoDB,
-} from './singleton';
+// Singleton pattern removed - use factory functions instead