DC-012: Add Kubernetes-style /healthz + /readyz probe aliases

Fresh users copy-pasting healthcheck blocks from k8s/Docker docs need
the standard short aliases. Without /healthz and /readyz they get
connection refused. This commit:

1. Adds /healthz + /readyz as root-level aliases for /health/live +
   /health/ready in src/app.js. Handler bodies DRYed into named
   functions (livenessHandler, readinessHandler) so a probe semantics
   change updates all five paths at once.

2. Removes the dead /api/v1/health*, /api/v1/health/live, /api/v1/health/ready
   registrations from PUBLIC_ROUTES and CSRF exclusion list — those
   routes were never actually mounted on the apiRouter (only root
   paths existed). Anyone probing /api/v1/health now gets a clean 404
   instead of being routed through to a duplicate root handler.

3. Adds bypass for the 5 probe paths in three places where it matters:
   - PUBLIC_ROUTES (no auth)
   - csrf-protection.js excludedPaths (no CSRF check)
   - middleware.js request-logging exclusion (k8s polling every 10s
     doesn't flood the audit log)
   - middleware.js Tailscale auth bypass (probes don't carry Tailscale
     identity headers)

4. Adds __tests__/health-probe-aliases.test.js (19 tests):
   - Alias equivalence (/healthz == /health/live, /readyz == /health/ready)
   - Back-compat (/health == /health/live)
   - Path consolidation (all 3 /api/v1/health* return 404)
   - Source-of-truth PUBLIC_ROUTES allowlist sync check
   - Source-of-truth src/app.js mount list sync check (catches drift
     between handler mount and middleware allowlist)

5. Documents probes in README (copy-paste docker-compose.yml +
   Kubernetes blocks) and user-guide (Health Probes section + System
   API table updated).

Post-fix: 941/941 tests pass (+19 new). Zero new ESLint warnings
introduced. The pre-existing warnings/errors in src/app.js line 906
('os' is not defined) and the empty blocks in logging.test.js are
not regressions from this commit.

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **TOTP recovery system (4-part defense against permanent lockout).** Pre-lockout: `.bak` fallback credentials file checked at every TOTP init, used silently when primary fails. Diagnostic: `/recovery-info` endpoint + `/recovery-panel` UI on the entry screen with one-click "Import Backup" + "Download Backup" buttons. Post-lockout: friction-free `.license-secret` restore flow. (`d230b39`, `3dff49c`, `7bbd969`)
 
 ### Added
+- **Kubernetes-standard health probe aliases (DC-012).** Added `/healthz` and `/readyz` as root-level aliases for `/health/live` and `/health/ready` so fresh users can copy-paste `healthcheck:` blocks from k8s/Docker docs. Liveness (`/healthz`) is a pure process check — no I/O. Readiness (`/readyz`) checks the config file, services file, Docker daemon, and Caddy admin API (3s timeout each), returning 200 if all OK or 503 with a `checks` object detailing failures. Both endpoints are unauthenticated by design (orchestration tooling doesn't carry session cookies). Probe endpoints also bypass CSRF validation and are excluded from per-request logging so k8s polling every 10s doesn't flood the audit log. Added `__tests__/health-probe-aliases.test.js` (19 tests) — covers alias equivalence, the removed `/api/v1/health` returning 404, and a source-of-truth sync test that detects drift between `src/app.js` mount list and `src/utilities/middleware.js` allowlist. README and user-guide updated with copy-paste `docker-compose.yml` and Kubernetes probe blocks.
 - **OpenClaw routes** — full set under `/openclaw` prefix: connect, disconnect, status, host discovery. `docker.client` wrapper fixed; duplicate `/apps/` paths stripped across sub-routers.
 - **Auto-backup scheduling (premium tier)** + storage-limit enforcement (prune oldest when `maxStorageBytes` exceeded) + restore-from-backup on update rollback. Bundled workflows included out-of-the-box.
 - **Monitoring widget on main dashboard** — CPU/mem data flattened, health summary added; `/api/monitoring/stats` exposed as a public route with rate-limit.
@@ -35,6 +36,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **Updater false-positive loop** when commit hash was unknown — fixed.
 
 ### Removed
+- **Dead `/api/v1/health`, `/api/v1/health/live`, `/api/v1/health/ready` routes** (DC-012) — these were registered in `PUBLIC_ROUTES` and CSRF exclusion lists but never actually mounted on the apiRouter. Consolidated to root-level `/health`, `/health/live`, `/health/ready` plus new `/healthz` and `/readyz` aliases. Anyone probing `/api/v1/health` will now get a clean 404 instead of an unexpected behaviour.
 - Stale ad-hoc test/debug scripts (`comprehensive-test.js`, `test-security-fixes.js`) moved to `dashcaddy-api/scripts/legacy/` (preserved, not deleted — 875 lines of security test coverage retained as a manual smoke test).
 - Stale root-level files: `*.bak`, `server-old.js`, and ad-hoc reports (`DEPLOYMENT-SUCCESS.md`, `FINAL-DEPLOYMENT-REPORT.md`, `DESLOPIFICATION-ROADMAP.md`, etc.) — disk-only cleanup, already gitignored.
 - Dead `routes/` directory at API root (replaced by `src/routes/`).