[Studio] Validate ACL delete requests

[Aias00]

Summary

• replace ACL rule/user delete map parsing with a typed request DTO
• validate required ids before invoking ACL delete operations
• return structured 400 responses for missing or blank ACL delete ids

Scope

• RocketMQ Studio contest scope: Track 1 / AUTH-01 ACL management hardening
• Does not introduce Namespace behavior

Tests

• JAVA_HOME=/Users/aias/Library/Java/JavaVirtualMachines/openjdk-21.0.2/Contents/Home mvn -q -Dtest=AclControllerTest,AclServiceTest test
• JAVA_HOME=/Users/aias/Library/Java/JavaVirtualMachines/openjdk-21.0.2/Contents/Home mvn -q test
• git diff --check

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[Aias00]

Superseded by #636. Consolidated with related ACL request validation changes to reduce review overhead while preserving the same scoped fixes and tests.