App 2.20.0: lease mileage allowance on the Overview

Vehicle info shows the km allowed by today (40,000 km over four years
from 2023-05-01, evenly per day) and the odometer against it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LhzAVaUyqcw5PkGjz4mWW6

app/src/test/java/com/evsuite/abrp/LeaseAllowanceTest.java

@@ -0,0 +1,36 @@
+package com.evsuite.abrp;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import java.time.LocalDate;
+
+import org.junit.Test;
+
+/** The lease mileage allowance — pure JVM. */
+public class LeaseAllowanceTest {
+
+    @Test
+    public void accruesEvenlyPerDay() {
+        assertEquals(0d, LeaseAllowance.allowedKm(LocalDate.of(2023, 5, 1)), 1e-9);
+        // 731 of 1461 days (2024 is a leap year).
+        assertEquals(40_000d * 731 / 1461, LeaseAllowance.allowedKm(LocalDate.of(2025, 5, 1)), 1e-9);
+        assertEquals(40_000d, LeaseAllowance.allowedKm(LocalDate.of(2027, 5, 1)), 1e-9);
+    }
+
+    @Test
+    public void staysWithinTheLease() {
+        assertEquals(0d, LeaseAllowance.allowedKm(LocalDate.of(2023, 1, 1)), 1e-9);
+        assertEquals(40_000d, LeaseAllowance.allowedKm(LocalDate.of(2028, 1, 1)), 1e-9);
+    }
+
+    @Test
+    public void differenceIsOverPositiveUnderNegative() {
+        LocalDate day = LocalDate.of(2025, 5, 1);
+        double allowed = LeaseAllowance.allowedKm(day);
+        assertEquals(1000d, LeaseAllowance.differenceKm((float) (allowed + 1000), day), 0.01);
+        assertEquals(-500d, LeaseAllowance.differenceKm((float) (allowed - 500), day), 0.01);
+        assertNull(LeaseAllowance.differenceKm(null, day));
+        assertNull(LeaseAllowance.differenceKm(Float.NaN, day));
+    }
+}