fix(api): accept academic-year codes in rankings year filter

The rankings endpoint validated year with le=2100, but the database
stores academic-year codes like 201819, so any explicit year selection
returned a 422 and the rankings page rendered its empty state. Widen
the bound to cover the codes and extend the e2e journey to pick a
specific year and assert the table stays populated.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/app.py

@@ -834,7 +834,10 @@ async def get_rankings(
     request: Request,
     metric: str = Query("rwm_expected_pct", description="Metric to rank by", max_length=50),
     year: Optional[int] = Query(
-        None, description="Specific year (defaults to most recent)", ge=2000, le=2100
+        None,
+        description="Academic year code, e.g. 201819 (defaults to most recent)",
+        ge=2000,
+        le=210100,
     ),
     limit: int = Query(20, ge=1, le=100, description="Number of schools to return"),
     local_authority: Optional[str] = Query(

e2e/tests/journeys.spec.ts

@@ -73,3 +73,21 @@ test('rankings page loads a populated table', async ({ page }) => {
   await expect(rows.first()).toBeVisible({ timeout: 15_000 });
   expect(await rows.count()).toBeGreaterThan(5);
 });
+
+test('rankings stay populated after picking a specific year', async ({ page }) => {
+  // Years are academic-year codes (e.g. 201819); the API must accept them
+  // as the `year` query param rather than rejecting with a 422.
+  await page.goto('/rankings');
+  const yearSelect = page.locator('#year-select');
+  await expect(yearSelect).toBeVisible({ timeout: 15_000 });
+
+  // Pick the first explicit year option (index 0 is the "Latest" default).
+  const yearValue = await yearSelect.locator('option').nth(1).getAttribute('value');
+  expect(yearValue).toBeTruthy();
+  await yearSelect.selectOption(yearValue!);
+  await page.waitForURL(/year=/);
+
+  const rows = page.locator('table tbody tr');
+  await expect(rows.first()).toBeVisible({ timeout: 15_000 });
+  expect(await rows.count()).toBeGreaterThan(5);
+});