fix(prediction): correct lon mapping

tests/e2e/dataset-param.spec.ts

@@ -0,0 +1,77 @@
+import { test, expect, login } from './fixtures';
+
+/**
+ * The client must not invent a dataset.
+ *
+ * `predictionsApi.run` used to fall back to a client-side guess at which GFS run
+ * the server held, and the guess had rotted into a hardcoded "2025-04-06T00:00:00Z"
+ * — over a year stale. That was harmless only for as long as Django dropped the
+ * parameter on the floor. Now that the predictor honours it and refuses a run it
+ * does not hold, sending an invented epoch fails every prediction with
+ * "dataset 2025-04-06T00:00:00Z is not stored".
+ *
+ * Which runs exist is server knowledge. An unchosen dataset must stay absent so
+ * the server picks.
+ */
+
+test.beforeEach(async ({ context }) => {
+	await login(context);
+});
+
+test('a prediction request carries no dataset the operator did not choose', async ({ page }) => {
+	test.setTimeout(120_000);
+
+	const bodies: string[] = [];
+	await page.route('**/predictions/', async (route) => {
+		if (route.request().method() === 'POST') {
+			bodies.push(route.request().postData() ?? '');
+		}
+		await route.continue();
+	});
+
+	await page.goto('/');
+	await page.evaluate(() => {
+		const ws = {
+			id: crypto.randomUUID(),
+			name: 'dataset-param',
+			color: '#dc3545',
+			opacity: 1,
+			visible: true,
+			flightParameters: {
+				ascent_rate: 5,
+				burst_altitude: 30000,
+				dataset: '', // the UI's "choose automatically"
+				descent_rate: 5,
+				format: 'json',
+				launch_altitude: 0,
+				launch_latitude: 52.2,
+				launch_longitude: 0.1,
+				profile: 'standard_profile',
+				version: 2,
+			},
+			launchDate: new Date().toISOString().split('T')[0],
+			launchTime: '12:00:00',
+			result: null,
+		};
+		localStorage.setItem('workspaces', JSON.stringify({ items: [ws], activeId: ws.id }));
+	});
+	await page.goto('/predict');
+	await page
+		.locator('.map-container canvas')
+		.first()
+		.waitFor({ state: 'attached', timeout: 60_000 });
+
+	await page
+		.locator('.panel-container-right .workspace-row')
+		.first()
+		.getByRole('button', { name: /Рассчитать|Run/ })
+		.click();
+
+	await expect.poll(() => bodies.length, { timeout: 60_000 }).toBeGreaterThan(0);
+
+	const payload = JSON.parse(bodies[0]);
+	expect(payload).not.toHaveProperty('dataset');
+	// The rest of the request must still be intact.
+	expect(payload.launch_latitude).toBe(52.2);
+	expect(payload.launch_datetime).toBeTruthy();
+});