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/src/lib/prescription-validation.ts

@@ -0,0 +1,26 @@
+import { z } from "zod";
+
+const nonEmpty = z.string().trim().min(1);
+
+// Payload accepted by POST/PUT /api/prescriptions. The frontend dialog omits
+// prescriber / prescribedAt / status on create — the route fills the prescriber
+// from the signed-in user, the DB defaults prescribedAt to today, and status
+// defaults to "active".
+export const prescriptionInputSchema = z.object({
+  fileNumber: z.string().trim().default(""),
+  name: nonEmpty.max(200),
+  initials: z.string().trim().min(1).max(4),
+  medication: nonEmpty.max(200),
+  dose: z.string().trim().max(120).default(""),
+  frequency: nonEmpty.max(120),
+  prescriber: z.string().trim().max(200).default(""),
+  prescribedAt: z
+    .string()
+    .regex(/^\d{4}-\d{2}-\d{2}$/, "Date must be YYYY-MM-DD.")
+    .optional(),
+  status: z.enum(["active", "completed", "expired"]).default("active"),
+  duration: z.string().trim().max(120).nullish(),
+  notes: z.string().max(5000).nullish(),
+});
+
+export type PrescriptionInput = z.infer<typeof prescriptionInputSchema>;