Prepare release 4.7.6

[WRRicht3r]

Summary

• Release 4.7.6 changelog

SCCP Sensitive Path Impact

• This PR touches one or more SCCP-sensitive paths:
  • pallets/sccp/
  • runtime/src/lib.rs
  • runtime/src/tests/sccp_runtime_integration.rs
  • misc/sccp-mcp/
  • docs/security/

If checked above:

• Requested at least 2 reviewers.
• At least 1 reviewer is familiar with SCCP threat model and finality assumptions.
• Completed the SCCP security checklist below.

SCCP Security Checklist

• Does this change expand externally reachable functionality?
• Are defaults still fail-closed / least-privilege?
• Are new or modified tools covered by allow/deny policy behavior?
• Are runtime weights and benchmark assumptions still valid?
• Are tests updated for both success and expected-failure paths?

Test Evidence

• List exact commands run and key pass/fail results.

[WRRicht3r]

Published the v4.7.6 release artifacts:

• Tag: https://github.com/sora-xor/sora2-network/releases/tag/v4.7.6
• Notes: copied from RELEASE_NOTES.md in this PR.

Let me know if you also need build artifacts attached.