docs: update README + CHANGELOG for 2026-06-22 audit batch

[bashrusakh]

Summary

• README: new Project status block (DB v272, CodeQL state, last audit cycle), ServerHealth/sidebar bullets in admin-ui state, expanded feature matrix to cover encrypted-at-rest secrets, server-cmd audit/persistence, Linux/Android GitHub Actions route, capability-URL TTL, profile self-edit.
• CHANGELOG: new [Unreleased] - 2026-06-22 section grouping the 18 fix branches merged via PR chore: batch-merge 18 fix branches into main (DB→272) #30 plus the security chain (PRs fix(security): resolve all 47 CodeQL alerts #24–api(lib/upload): fix SSRF in callback public-key fetch #29). Covers the 269→272 DB-version step, CodeQL remediations, custom-builder hardening, admin server-command audit + persistence, rdgen production-guard, and admin-ui fixes.

Test plan

• Render README on GitHub — check the new Project status block, feature matrix, screenshots row.
• Skim CHANGELOG [Unreleased] - 2026-06-22 for accuracy against BUGS.md IDs and merged PRs.