fix: Chunk kind-5 deletion events in deleteDeprecatedKind4 to avoid relay payload limits

[coderabbitai]

Summary

In js/actions.js, deleteDeprecatedKind4() currently packs all collected kind-4 event IDs into a single kind-5 deletion event. On accounts with large NIP-04 DM histories, this single event can exceed relay payload/message size limits, causing silent total failure of the cleanup operation.

Problem

A single kind-5 event with thousands of e tags may be rejected by relays that enforce maximum message size constraints, with no partial success — the entire deletion silently fails.

Expected Behavior

Kind-5 deletion events should be chunked into smaller batches so that relay payload limits are respected and partial progress is possible even if some batches fail.

References

• PR: feat: Operating Room, guided treatment, doctor recommendations & UI overhaul #15
• Review comment: feat: Operating Room, guided treatment, doctor recommendations & UI overhaul #15 (comment)

Requested by @dannym-arx