[grade=A urn:ump:seyasvbntxsjibq5jiaqmfowc6xgchwe4jvcc54jd6355ujgm75q] DC-122: self-updater hardening + auto-update on + docker disk discipline (v1.16.0)

- _isNewer: same-version releases are never 'newer' (commit labels are
  opaque stamps) — kills the same-version auto-apply regression loop
- _autoCheckAndApply: identical version@sha256 never re-applied
- dashcaddy-update.sh: truthful rollback verdicts (failed rebuild/health
  = exit 1 + failure result), exact frontend snapshot/restore (incl.
  update-introduced owned subtrees), contents-copy cp fallbacks with
  manifest reconciliation, JSON-encoded results/meta/stamp, prune on
  every exit path
- self-updater: frontend-only Linux releases fail loudly (no more silent
  no-op success stuck in 'applying')
- start.sh: DASHCADDY_UPDATE_ENABLED=true (Sami 2026-09-13), json-file
  log caps 10M x3, source->webroot sync via update-stamp contract
- tests: _isNewer regression suite, functional cycle + json/escape suites
  (scripts/test-frontend-cycle.sh, scripts/test-json-escape.sh)

15 judge rounds: C,C,D,D,C,C,D,C,C,C,D,C,A

dashcaddy-api/package.json

@@ -1,6 +1,6 @@
 {
   "name": "dashcaddy-api",
-  "version": "1.15.0",
+  "version": "1.16.0",
   "description": "DashCaddy API server - Dashboard backend for Docker, Caddy & DNS management",
   "main": "server.js",
   "engines": {