chore(release): v1.4.38

Robustness sweep, perf hotspots, full localization, coach gate
cascade closure. See CHANGELOG.md for the full set; headline:

- /api/dashboard/summary cold-mount 4.6 s → ~500 ms via DAY-bucket
  sparkline + 60 s response cache.
- Coach API gate inventory test surfaced and closed two orphan
  routes (chat[id] GET+DELETE, chat-message feedback POST).
- Cross-tz fast-path runtime guard falls back to live for users
  more than ±3 h from UTC; proper bucket minting stays v1.5.
- es / fr / it / pl coverage 27 % → 63 % (~3 400 new strings) plus
  three medication-cluster placeholder restorations.
- IANA timezone validation closes the User.timezone self-DoS
  regression the new dashboard SQL would have surfaced.
- Unit suite 4520 → 4524.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "healthlog",
-  "version": "1.4.37.2",
+  "version": "1.4.38",
   "description": "Self-hosted personal-health-tracking PWA with Withings integration, AI insights, and doctor-report PDF export.",
   "license": "AGPL-3.0-only",
   "homepage": "https://healthlog.dev",