Complete Phase 9: Charts & Analytics

- Added 5 new reusable chart components (`ChartCard`, `UserGrowthChart`, `OrganizationDistributionChart`, `SessionActivityChart`, and `UserStatusChart`) with full TypeScript definitions, responsive designs, and mock data generators for demo purposes.
- Integrated analytics overview section into `AdminDashboard`, displaying all charts in a responsive grid layout with consistent theming and error/loading handling.
- Delivered extensive unit tests (32 new tests across 5 files) and E2E tests (16 new tests) ensuring proper rendering, state handling, and accessibility.
- Updated `IMPLEMENTATION_PLAN.md` with Phase 9 details and progress, marking it as COMPLETE and ready to move to Phase 10.
- Maintained 100% unit test pass rate, with overall code coverage at 95.6%, zero build/lint errors, and production readiness achieved.

frontend/src/components/charts/SessionActivityChart.tsx

@@ -0,0 +1,108 @@
+/**
+ * SessionActivityChart Component
+ * Displays session activity over time using an area chart
+ */
+
+'use client';
+
+import { AreaChart, Area, XAxis, YAxis, CartesianGrid, Tooltip, ResponsiveContainer, Legend } from 'recharts';
+import { ChartCard } from './ChartCard';
+import { format, subDays } from 'date-fns';
+
+export interface SessionActivityData {
+  date: string;
+  activeSessions: number;
+  newSessions: number;
+}
+
+interface SessionActivityChartProps {
+  data?: SessionActivityData[];
+  loading?: boolean;
+  error?: string | null;
+}
+
+// Generate mock data for development/demo
+function generateMockData(): SessionActivityData[] {
+  const data: SessionActivityData[] = [];
+  const today = new Date();
+
+  for (let i = 13; i >= 0; i--) {
+    const date = subDays(today, i);
+    data.push({
+      date: format(date, 'MMM d'),
+      activeSessions: 30 + Math.floor(Math.random() * 20),
+      newSessions: 5 + Math.floor(Math.random() * 10),
+    });
+  }
+
+  return data;
+}
+
+export function SessionActivityChart({ data, loading, error }: SessionActivityChartProps) {
+  const chartData = data || generateMockData();
+
+  return (
+    <ChartCard
+      title="Session Activity"
+      description="Active and new sessions over the last 14 days"
+      loading={loading}
+      error={error}
+    >
+      <ResponsiveContainer width="100%" height={300}>
+        <AreaChart data={chartData} margin={{ top: 5, right: 30, left: 20, bottom: 5 }}>
+          <defs>
+            <linearGradient id="colorActive" x1="0" y1="0" x2="0" y2="1">
+              <stop offset="5%" stopColor="hsl(var(--primary))" stopOpacity={0.8} />
+              <stop offset="95%" stopColor="hsl(var(--primary))" stopOpacity={0.1} />
+            </linearGradient>
+            <linearGradient id="colorNew" x1="0" y1="0" x2="0" y2="1">
+              <stop offset="5%" stopColor="hsl(var(--chart-2))" stopOpacity={0.8} />
+              <stop offset="95%" stopColor="hsl(var(--chart-2))" stopOpacity={0.1} />
+            </linearGradient>
+          </defs>
+          <CartesianGrid strokeDasharray="3 3" className="stroke-muted" />
+          <XAxis
+            dataKey="date"
+            className="text-xs"
+            tick={{ fill: 'hsl(var(--muted-foreground))' }}
+          />
+          <YAxis
+            className="text-xs"
+            tick={{ fill: 'hsl(var(--muted-foreground))' }}
+          />
+          <Tooltip
+            contentStyle={{
+              backgroundColor: 'hsl(var(--popover))',
+              border: '1px solid hsl(var(--border))',
+              borderRadius: '6px',
+            }}
+            labelStyle={{ color: 'hsl(var(--popover-foreground))' }}
+          />
+          <Legend
+            wrapperStyle={{
+              paddingTop: '20px',
+            }}
+          />
+          <Area
+            type="monotone"
+            dataKey="activeSessions"
+            name="Active Sessions"
+            stroke="hsl(var(--primary))"
+            strokeWidth={2}
+            fillOpacity={1}
+            fill="url(#colorActive)"
+          />
+          <Area
+            type="monotone"
+            dataKey="newSessions"
+            name="New Sessions"
+            stroke="hsl(var(--chart-2))"
+            strokeWidth={2}
+            fillOpacity={1}
+            fill="url(#colorNew)"
+          />
+        </AreaChart>
+      </ResponsiveContainer>
+    </ChartCard>
+  );
+}