feat: add modular services and repositories for improved code organization

Introduce repository pattern across multiple services, including `favorites`, `tags`, `sessions`, `reports`, `auth`, and more. Decouple crypto functionalities into modular services like `HashingService`, `JwtService`, and `EncryptionService`. Improve testability and maintainability by simplifying dependencies and consolidating utility logic.

backend/src/crypto/crypto.module.ts

@@ -1,8 +1,24 @@
 import { Module } from "@nestjs/common";
 import { CryptoService } from "./crypto.service";
+import { HashingService } from "./services/hashing.service";
+import { JwtService } from "./services/jwt.service";
+import { EncryptionService } from "./services/encryption.service";
+import { PostQuantumService } from "./services/post-quantum.service";
 
 @Module({
-	providers: [CryptoService],
-	exports: [CryptoService],
+	providers: [
+		CryptoService,
+		HashingService,
+		JwtService,
+		EncryptionService,
+		PostQuantumService,
+	],
+	exports: [
+		CryptoService,
+		HashingService,
+		JwtService,
+		EncryptionService,
+		PostQuantumService,
+	],
 })
 export class CryptoModule {}