release: 2.4.1: code audit of 2.4.0 and its plan

Docs only. docs/audit-2026-10-12.md: findings of a full-tree audit (four
high, twenty-one medium, the rest), doc drift, test gaps, what was checked
and found sound, and a six-stage plan; roadmap index row; CHANGELOG cut and
pin bump. Old tags and images stay as they are (owner): fixes go forward.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/guide.md

@@ -184,7 +184,7 @@ cat ./data/setup-token
 #### Fixed image tag
 
 `deploy/docker-compose.yml` pins an explicit version (`ghcr.io/mixeme/selfpost:X.Y.Z`),
-deliberately never `:latest`. The current pin is `2.4.0`. Intermediate
+deliberately never `:latest`. The current pin is `2.4.1`. Intermediate
 CHANGELOG sections (`0.2.0`…`0.6.0`) record development cuts from before that
 image was published. Pinning matters because of the backup version check (see
 [Full backup and restore](#full-backup-and-restore)): the panel binary's