feat: complete analytics category filtering

backend/src/services/analytics.integration.test.ts

@@ -32,6 +32,8 @@ async function testQueries(): Promise<void> {
     const params = { from: '2026-07-01', to: '2026-07-31', accountId, onlyConfirmed: true };
     const summary = await getSummary(params, client);
     assert.deepEqual({ expense: summary.totalExpense, income: summary.totalIncome, net: summary.net, transferOut: summary.transferOutflow, interest: summary.interestIncome }, { expense: 6_000, income: 15_000, net: 9_000, transferOut: 3_000, interest: 1_500 });
+    const categorySummary = await getSummary({ ...params, categoryId: categoryId.expense }, client);
+    assert.deepEqual({ expense: categorySummary.totalExpense, income: categorySummary.totalIncome }, { expense: 6_000, income: 0 });
     assert.equal((await getSummary({ ...params, from: '2026-08-01', to: '2026-08-31' }, client)).totalExpense, 7_000);
     assert.deepEqual((await getByCategory(params, client)).map((item) => item.amount), [6_000]);
     const timeseries = await getTimeseries({ ...params, granularity: 'month' }, client);

backend/src/services/analytics.ts

@@ -14,6 +14,7 @@ interface BaseParams {
   from: string;
   to: string;
   accountId?: number;
+  categoryId?: number;
   onlyConfirmed?: boolean;
 }
 
@@ -61,6 +62,11 @@ function buildBaseConditions(
     values.push(params.accountId);
     idx++;
   }
+  if (params.categoryId != null) {
+    conditions.push(`t.category_id = $${idx}`);
+    values.push(params.categoryId);
+    idx++;
+  }
   if (params.onlyConfirmed) {
     conditions.push('t.is_category_confirmed = TRUE');
   }