Add Serialize/Deserialize derives to DeduplicationKey

[jason-h23]

Summary

DeduplicationKey in src/sentinel/alert.rs only derives Debug, Clone, PartialEq, Eq, Hash. Adding Serialize and Deserialize enables persisting dedup state across restarts and structured logging.

What To Do

Add Serialize and Deserialize derive macros to the DeduplicationKey struct (line 137).

Files

• src/sentinel/alert.rs (lines 137-141)

Acceptance Criteria

• Serialize and Deserialize added to derives
• All existing tests pass
• Clippy passes

Estimated Effort

1-2 line change, ~15 minutes