fix(forms): send one Idempotency-Key per opened create form

A mood, symptom, lab value, custom metric value, unscheduled dose,
allergy, vaccination, visit or measurement saved on a weak signal could
be stored twice: the POST committed, the answer missed the 15 s
timeout, the form said it could not save, and the second tap was a new
call with a new key, so the server ran it again.

useIdempotentPost keeps one key until a save lands and renews it for the
next entry, so the retry replays the first answer. The create forms and
the three create hooks post through it; the comment on the per-call key
in api-fetch now says what that key does and does not cover.

LabForm and MoodForm each gain the one line that mounts the key, so
their function-size baselines go up by one. The intake toast guard now
recognises a dose posted through the hook.

src/components/labs/lab-form.tsx

@@ -21,7 +21,8 @@ import {
   SelectValue,
 } from "@/components/ui/select";
 import { Textarea } from "@/components/ui/textarea";
-import { apiGet, apiPost } from "@/lib/api/api-fetch";
+import { apiGet } from "@/lib/api/api-fetch";
+import { useIdempotentPost } from "@/lib/api/use-idempotent-post";
 import { localizedApiError } from "@/lib/api/localized-error";
 import {
   isUnreadableRange,
@@ -144,6 +145,7 @@ export function LabForm({
   const labNumber = useLabNumber();
   const recordName = useActiveRecordName();
   const queryClient = useQueryClient();
+  const post = useIdempotentPost();
   const formId = useId();
 
   const { data: catalog, isLoading: catalogLoading } = useQuery({
@@ -265,7 +267,7 @@ export function LabForm({
       const printed = isQualitative
         ? null
         : parseReferenceRange(sourceRange, selected?.unit);
-      const created = await apiPost<LabResultDto>("/api/labs", {
+      const created = await post<LabResultDto>("/api/labs", {
         biomarkerId,
         ...(isQualitative
           ? { valueText: qualitativeValue }