[amitfin]

• Harden async TCP/UDP shutdown behavior and clean server lifecycle management; add extra logging for TCP event flow.
• Add response_qualifier to SIAAccount and include it in ACK/NAK/encrypted responses.
• Use a default account fallback when the exact account ID is missing.
• Improve ADM-CID parsing to return a default code for unknown types.
• Add tests covering response qualifier behavior, default account fallback, and shutdown handling for sync/async servers.
• Devcontainer/VS Code config tweaks for port mapping and debug configs.