feat(analysis): add trend charts to the Analysis page

The Analysis page only showed KPI numbers. Add two real time-series and render
them as dependency-free bar charts (matching components/chat/sparkline.tsx):

- backend: GET /api/analytics now returns `trends.patientsByMonth` (new patients
  per month over the last 6 months) and `trends.appointmentsByWeekday`
  (appointments per day for the current week), bucketed in JS from one query each.
- frontend: new components/analysis/bar-chart.tsx and two chart sections on the
  Analysis view (Patient growth, Appointments this week), with i18n keys.

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

frontend/lib/i18n/locales/en/translation.json

@@ -402,6 +402,13 @@
       "description": "Care-team workload",
       "open": "Open",
       "completed": "Completed"
+    },
+    "charts": {
+      "patientGrowthTitle": "Patient growth",
+      "patientGrowthDescription": "New patients per month over the last 6 months",
+      "weeklyAppointmentsTitle": "Appointments this week",
+      "weeklyAppointmentsDescription": "Bookings per day for the current week",
+      "empty": "No data yet"
     }
   },
   "activity": {