fix(inventory): serialise unknown units as null, not 0 (iOS shows unknown, no phantom negatives)

docs/api/openapi.yaml

@@ -11992,14 +11992,21 @@ components:
           description: Kind of physical container (PEN / AMPOULE / BLISTER / INHALER / BOTTLE / OTHER). Display-level
             classification; defaults to OTHER.
         unitsTotal:
-          type: number
+          anyOf:
+            - type: number
+            - type: "null"
           description: Units the container shipped with (tablets / ampoules / puffs; 1–1000). v1.16.12 — fractional, so a
-            split-pill remainder reads cleanly. Dose-derived readouts divide by the medication's `unitsPerDose`.
+            split-pill remainder reads cleanly. Dose-derived readouts divide by the medication's `unitsPerDose`. v1.18.3
+            (iOS#31) — NULL when the unit count is unknown (a corrupt or legacy row); the client renders "unknown",
+            never a fabricated 0.
         unitsRemaining:
-          type: number
+          anyOf:
+            - type: number
+            - type: "null"
           description: Units left in the container. v1.16.12 — fractional (a ½-tablet dose leaves 29.5 of 30). Decremented by the
             intake consumption hook (FEFO with spillover across containers); refunded when a taken dose is skipped,
-            edited away, or deleted.
+            edited away, or deleted. v1.18.3 (iOS#31) — NULL when the count is unknown (a corrupt or legacy row); the
+            client renders "unknown", never a fabricated 0 it could decrement into negatives.
         firstUseAt:
           anyOf:
             - type: string