backend: org-scoped pharmacy inventory model

Add an `inventory` resource mirroring the prescriptions feature end-to-end:
Drizzle table (org-scoped, indexed), domain type, zod validation, service
(list/get/create/update/delete), and an RBAC-gated CRUD router mounted at
/api/inventory. Grant the new `inventory` statement to roles — pharmacy gets
read/write, full clinicians read/write/delete, reception/lab none — in both the
backend access control and (mirrored) the frontend. Record writes in the
activity log via a new `inventory` entity type. Includes the migration and an
idempotent demo seed script.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/drizzle/meta/_journal.json

@@ -85,6 +85,13 @@
       "when": 1781196252617,
       "tag": "0011_remap_viewer_to_member",
       "breakpoints": true
+    },
+    {
+      "idx": 12,
+      "version": "7",
+      "when": 1781279151289,
+      "tag": "0012_wonderful_terrax",
+      "breakpoints": true
     }
   ]
 }