test: real backend pytest + E2E Playwright suites, both isolated from prod data

backend/tests/: 33 pytest tests against a real Postgres database
(aurum_test, created/migrated/dropped per run) exercised through the actual
HTTP API — not sqlite, not mocks, and the real `aurum` database is never
opened (app lifespan is skipped, get_session is overridden per test).
Covers transaction category-kind validation, year/month/date-range
filtering and pagination, dashboard summary arithmetic, budget status, cash
flow, and the /transactions/years picker.

e2e/: 6 Playwright specs driving a real browser against a fully separate
throwaway docker-compose stack (run.sh: separate project name, database,
port, and volume, torn down with `down -v` on exit) — regression coverage
for the Recent Transactions month bug, the Card grid-overflow bug, the
frozen-year bug, the Net Worth default range, and the Dashboard->
Transactions deep link, all fixed earlier this session.

Also synced the backend's APP_VERSION constant (stale at 0.15.2, embedded
in exported backups) with the frontend version.

e2e/tests/dashboard-recent-transactions.spec.ts

@@ -0,0 +1,38 @@
+import { test, expect } from "@playwright/test";
+import { createTransaction, getCategoryId, getDefaultAccountId } from "./helpers";
+
+// Regression for the Aug 2026 bug: RecentTransactionsCard queried
+// transactions without year/month at all, so switching the Dashboard's
+// month did nothing — it just showed the latest N transactions globally,
+// including ones from a completely different month. See UPDATES.md
+// (v0.15.3) and frontend/src/components/dashboard/RecentTransactionsCard.tsx.
+test("Recent Transactions on Dashboard only shows the selected month", async ({ page, request }) => {
+  const accountId = await getDefaultAccountId(request);
+  const categoryId = await getCategoryId(request, "Groceries");
+
+  await createTransaction(request, {
+    account_id: accountId,
+    category_id: categoryId,
+    type: "expense",
+    amount: "12.00",
+    description: "july-2015-only-txn",
+    date: "2015-07-26",
+  });
+  await createTransaction(request, {
+    account_id: accountId,
+    category_id: categoryId,
+    type: "expense",
+    amount: "34.00",
+    description: "august-2015-only-txn",
+    date: "2015-08-08",
+  });
+
+  await page.goto("/");
+  await page.getByRole("button", { name: /^\d{4}$/ }).first().click();
+  await page.getByRole("option", { name: "2015" }).click();
+  await page.getByRole("button", { name: "Авг", exact: true }).click();
+
+  const recentCard = page.locator("div.rounded-xl", { has: page.getByText("Последние транзакции", { exact: true }) });
+  await expect(recentCard.getByText("august-2015-only-txn")).toBeVisible();
+  await expect(recentCard.getByText("july-2015-only-txn")).toHaveCount(0);
+});