feat: org-scoped prescriptions backend, wire prescriptions page

Add the prescriptions table, validation, service and CRUD routes
(/api/prescriptions, RBAC-gated; prescriber defaults to the signed-in
clinician, prescribedAt to today) and the frontend data module. The page
now loads/persists real data and computes its status KPIs.

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

backend/drizzle/meta/_journal.json

@@ -22,6 +22,13 @@
       "when": 1780849813505,
       "tag": "0002_fluffy_longshot",
       "breakpoints": true
+    },
+    {
+      "idx": 3,
+      "version": "7",
+      "when": 1780850147682,
+      "tag": "0003_lame_rawhide_kid",
+      "breakpoints": true
     }
   ]
 }