feat(fhir): wire the German BfArM ATC locale toggle into the export route

The builder already accepts a germanAtc option that appends the BfArM ATC
URI after the WHO entry. Thread it from the health-record export route: an
explicit germanAtc flag on the selection payload wins, otherwise it derives
from a German-region locale. The WHO coding stays coding[0], byte-identical
and locale-independent, so a WHO-only consumer is unaffected.

Add the optional germanAtc field to the strict export selection schema and
regenerate the OpenAPI contract.

docs/api/openapi.yaml

@@ -148,6 +148,8 @@ paths:
                   type: boolean
                 includeAiSummary:
                   type: boolean
+                germanAtc:
+                  type: boolean
               required:
                 - format
               additionalProperties: false