Add changelog for v4.23.1

[g-despot]

Changelog for the v4.23.1 release. Covers the 15 PRs merged since the v4.23.0 tag: seven feature entries and seven fixes.

Each generative entry names its module explicitly, so nothing reads as a duplicate of the similarly worded text2vec-* entries in the 4.23.0 section.

Docs only. The Sphinx build passes with no new warnings.

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.53%. Comparing base (95b5d76) to head (bc545f4).
⚠️ Report is 105 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2156      +/-   ##
==========================================
+ Coverage   86.64%   88.53%   +1.88%     
==========================================
  Files         300      306       +6     
  Lines       23172    23633     +461     
==========================================
+ Hits        20077    20923     +846     
+ Misses       3095     2710     -385     

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