chore: add v2026.410.0 release notes for security release

## Summary

- Adds release notes for v2026.410.0 security release covering
GHSA-68qg-g8mg-6pr7
- Required before triggering the stable release workflow to publish
2026.410.0 to npm

## Context

The security advisory GHSA-68qg-g8mg-6pr7 was published on 2026-04-10
listing 2026.410.0 as the patched version, but only canary builds exist
on npm. The authz fix (PR paperclipai#3315) is already merged to master. This PR
adds release notes so the stable release workflow can be triggered.

## Test plan

- Verify release notes content is accurate
- Merge, then trigger release.yml workflow_dispatch with
source_ref=master, stable_date=2026-04-10, dry_run=false
- Confirm npm view paperclipai version returns 2026.410.0

Co-authored-by: Paperclip <noreply@paperclip.ing>

Author: cryppadotta