Record crashes on the device so "two weeks without one" can be checked

The milestone asks for two weeks in the living room without a crash. Nobody
reads logcat on a TV, and by the time someone says "it was gone yesterday"
the log has rotated — the criterion had no evidence behind it.

CrashLog keeps the last ten crashes in the app's own files: timestamp,
version, and the top of the stack. Nothing is sent anywhere. The settings
show either "Kein Absturz aufgezeichnet" or the newest one, and clicking
the row clears the record — so the two weeks start when you say they do.

Verified by crashing the app on purpose: the entry appears as
"26.08.2026 18:10 · 0.11.5" with the exception below it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/unit/CrashLogTest.kt

@@ -0,0 +1,47 @@
+package dev.castarr.tv
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class CrashLogTest {
+
+    @Test
+    fun `an entry names the time, the version and the top of the stack`() {
+        val error = IllegalStateException("Senderliste leer")
+        // 26.08.2026, 19:12 (MESZ)
+        val entry = CrashLog.render(1787764320000L, "0.12.0", error)
+        val lines = entry.lines()
+        assertTrue(lines.first().contains("0.12.0"))
+        assertTrue(lines.first().contains("26.08.2026"))
+        assertTrue(entry.contains("IllegalStateException"))
+        assertTrue(entry.contains("Senderliste leer"))
+    }
+
+    @Test
+    fun `a long stack is cut down to something readable`() {
+        val error = RuntimeException("tief")
+        val entry = CrashLog.render(0L, "0.12.0", error)
+        // Kopfzeile plus höchstens TRACE_LINES Zeilen Stack.
+        assertTrue(entry.lines().size <= CrashLog.TRACE_LINES + 1)
+    }
+
+    @Test
+    fun `only the newest entries are kept`() {
+        val entries = (1..15).map { "Absturz $it" }
+        val kept = CrashLog.trim(entries)
+        assertEquals(CrashLog.KEEP, kept.size)
+        assertEquals("Absturz 15", kept.last())
+        assertEquals("Absturz 6", kept.first())
+    }
+
+    @Test
+    fun `blank entries are dropped instead of counting`() {
+        assertEquals(listOf("echt"), CrashLog.trim(listOf("", "  ", "echt")))
+    }
+
+    @Test
+    fun `nothing recorded stays nothing`() {
+        assertEquals(emptyList<String>(), CrashLog.trim(emptyList()))
+    }
+}