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>

frontend/lib/prescriptions.ts

@@ -0,0 +1,74 @@
+import { apiFetch } from "@/lib/api-client";
+
+// A prescription. Mirrors the backend `src/types/prescription.ts`. Scoped to the
+// active clinic. `prescribedAt` is an ISO YYYY-MM-DD date.
+export type RxStatus = "active" | "completed" | "expired";
+
+export type Prescription = {
+  id: string;
+  fileNumber: string;
+  name: string;
+  initials: string;
+  medication: string;
+  dose: string;
+  frequency: string;
+  prescriber: string;
+  prescribedAt: string; // YYYY-MM-DD
+  status: RxStatus;
+  duration: string | null;
+  notes: string | null;
+  createdAt: string;
+  updatedAt: string;
+};
+
+// The fields the "New prescription" dialog collects; the backend fills the
+// prescriber (from the signed-in user), prescribedAt (today) and status.
+export type PrescriptionInput = {
+  fileNumber: string;
+  name: string;
+  initials: string;
+  medication: string;
+  dose: string;
+  frequency: string;
+  duration?: string | null;
+  notes?: string | null;
+  prescriber?: string;
+  prescribedAt?: string;
+  status?: RxStatus;
+};
+
+// "2026-06-05" -> "Jun 5, 2026" (matches the previous mock display format).
+export function formatPrescribedAt(iso: string): string {
+  return new Date(`${iso}T00:00:00`).toLocaleDateString("en-US", {
+    month: "short",
+    day: "numeric",
+    year: "numeric",
+  });
+}
+
+export function listPrescriptions(): Promise<Prescription[]> {
+  return apiFetch<Prescription[]>("/api/prescriptions");
+}
+
+export function createPrescription(
+  input: PrescriptionInput,
+): Promise<Prescription> {
+  return apiFetch<Prescription>("/api/prescriptions", {
+    method: "POST",
+    body: JSON.stringify(input),
+  });
+}
+
+export function updatePrescription(
+  id: string,
+  input: PrescriptionInput,
+): Promise<Prescription> {
+  return apiFetch<Prescription>(`/api/prescriptions/${id}`, {
+    method: "PUT",
+    body: JSON.stringify(input),
+  });
+}
+
+export function deletePrescription(id: string): Promise<void> {
+  return apiFetch<void>(`/api/prescriptions/${id}`, { method: "DELETE" });
+}