feat: computed analytics endpoint, rework Analysis page

Add GET /api/analytics returning real aggregates over the clinic's
patients/appointments/prescriptions/tasks, and rebuild the Analysis page
to render them. Drops the fabricated revenue/profit cards — temetro has no
billing data source.

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

backend/src/types/analytics.ts

@@ -0,0 +1,23 @@
+// Server-computed clinic analytics returned by GET /api/analytics. All figures
+// are aggregates over the active clinic's real data (no fabricated financials).
+export type Analytics = {
+  patients: {
+    total: number;
+    newThisMonth: number;
+    active: number;
+  };
+  appointments: {
+    thisWeek: number;
+    completed: number;
+    cancelled: number;
+    upcoming: number;
+  };
+  prescriptions: {
+    total: number;
+    active: number;
+  };
+  tasks: {
+    open: number;
+    done: number;
+  };
+};