chore(release): v1.8.1 — multi-time medication compliance

Closes the two surfaces the 1.7.3 multi-time compliance fix did not
reach: the today-tile projection now mints one pending dose per
scheduled time, and the compliance heatmap classifies each dose against
its nearest scheduled time instead of the first window.

docs/api/openapi.yaml

@@ -1,7 +1,7 @@
 openapi: 3.1.0
 info:
   title: HealthLog API
-  version: 1.8.0
+  version: 1.8.1
   description: >-
     Self-hosted personal-health-tracking PWA — public API surface for the iOS native client and external ingest.