AetherGuard AI is presented as a holistic AI Trust & Integrity Gateway that expands the typical AI firewall paradigm to offer real-time semantic inspection, cryptographic accountability, responsible AI compliance, and robust operational governance. The system operates as a transparent reverse-proxy between LLM clients and providers, intercepting every prompt and response for multi-dimensional analysis before permitting egress or ingress. This paper makes the following primary contributions: A unified semantic firewall architecture integrating prompt security, responsible AI compliance, data privacy, model integrity, and operational governance in a single pipeline. A systematic threat taxonomy for LLM deployments with concrete mapping to open-source and cloud-native mitigation tools. A production-ready AWS reference implementation with multi-region support, sub-22 ms overhead, and a full DevOps blueprint. Empirical evaluation across security efficacy, latency, compliance, and operational usability dimensions.