chore(release): v1.28.20 — estimated drug level in efficacy + insights

The GLP-1 estimated active-substance curve (the modelled drug level from logged
doses) now also renders in the efficacy (Wirkung) tab and in the Insights
medication overview, not only under the injection tab. Both reuse the same
self-contained DrugLevelChart, gated on the GLP-1 treatment class, so the drug
level sits next to the efficacy readouts. Additive — no existing surface changes;
non-GLP-1 medications render nothing.

docs/api/openapi.yaml

@@ -1,7 +1,7 @@
 openapi: 3.1.0
 info:
   title: HealthLog API
-  version: 1.28.19
+  version: 1.28.20
   description: >-
     Self-hosted personal-health-tracking PWA — public API surface for the iOS native client and external ingest.