feat: overhaul stats dashboard with navigation, trends, and anime views

Add navigation state machine for tab/detail routing, anime overview
stats with Yomitan lookup rates, session word count accuracy fixes,
vocabulary tab hook order fix, simplified trends data fetching from
backend-aggregated endpoints, and improved session detail charts.

stats/src/lib/api-client.test.ts

@@ -65,3 +65,55 @@ test('deleteSession throws when the stats API delete request fails', async () =>
     globalThis.fetch = originalFetch;
   }
 });
+
+test('getTrendsDashboard requests the chart-ready trends endpoint with range and grouping', async () => {
+  const originalFetch = globalThis.fetch;
+  let seenUrl = '';
+  globalThis.fetch = (async (input: RequestInfo | URL) => {
+    seenUrl = String(input);
+    return new Response(
+      JSON.stringify({
+        activity: { watchTime: [], cards: [], words: [], sessions: [] },
+        progress: {
+          watchTime: [],
+          sessions: [],
+          words: [],
+          newWords: [],
+          cards: [],
+          episodes: [],
+          lookups: [],
+        },
+        ratios: { lookupsPerHundred: [] },
+        animePerDay: {
+          episodes: [],
+          watchTime: [],
+          cards: [],
+          words: [],
+          lookups: [],
+          lookupsPerHundred: [],
+        },
+        animeCumulative: {
+          watchTime: [],
+          episodes: [],
+          cards: [],
+          words: [],
+        },
+        patterns: {
+          watchTimeByDayOfWeek: [],
+          watchTimeByHour: [],
+        },
+      }),
+      { status: 200, headers: { 'Content-Type': 'application/json' } },
+    );
+  }) as typeof globalThis.fetch;
+
+  try {
+    await apiClient.getTrendsDashboard('90d', 'month');
+    assert.equal(
+      seenUrl,
+      `${BASE_URL}/api/stats/trends/dashboard?range=90d&groupBy=month`,
+    );
+  } finally {
+    globalThis.fetch = originalFetch;
+  }
+});