feat(settings): make medications a toggleable module

Medications graduated from the always-on core set (weight / blood
pressure / pulse stay core) to an opt-out module. The surface gates
off the resolved module map — the left-nav entry, the dashboard
medication widget, and the dedicated Medikamente settings entry hide
when the account turns the module off. The medication data routes stay
exempt from the gate (same data-layer reasoning as mood / labs): an
importer, a sync, and the user's ability to clean up entries keep
working while the surface is hidden, and re-enabling finds the
schedule and intake history intact.

Wire the module-route gate inventory, the dashboard widget/summary
maps, the PATCH allowlist, and the nav model; regenerate the OpenAPI
contract for the new module key.

docs/api/openapi.yaml

@@ -7076,6 +7076,8 @@ components:
           type: boolean
         insights:
           type: boolean
+        medications:
+          type: boolean
         doctorReport:
           type: boolean
       additionalProperties: false
@@ -12730,6 +12732,9 @@ components:
         insights:
           type: boolean
           description: Whether the "insights" module is enabled for this account.
+        medications:
+          type: boolean
+          description: Whether the "medications" module is enabled for this account.
         doctorReport:
           type: boolean
           description: Whether the "doctorReport" module is enabled for this account.
@@ -12745,6 +12750,7 @@ components:
         - achievements
         - coach
         - insights
+        - medications
         - doctorReport
       additionalProperties: false
       description: Fully-resolved per-user module enable/disable map. Every toggleable module key is present. `false` means