feat: use Worte/Weise labels and render metadata at page bottom (Closes #5)

Add metadata_labels ("abbreviated"/"german") and metadata_position
("top"/"bottom") options to LayoutConfig. German labels use "Worte:" and
"Weise:" instead of "T:" and "M:", with "Worte und Weise:" when lyricist
and composer are the same person. Metadata at bottom position renders
after notes with word-wrapping. MeasurementEngine accounts for two-line
metadata in German label mode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

parser/src/test/kotlin/de/pfadfinder/songbook/parser/ConfigParserTest.kt

@@ -214,6 +214,31 @@ class ConfigParserTest {
         config.toc.highlightColumn.shouldBeNull()
     }
 
+    @Test
+    fun `parse config with german metadata labels`() {
+        val yaml = """
+            book:
+              title: "Test"
+            layout:
+              metadata_labels: german
+              metadata_position: bottom
+        """.trimIndent()
+        val config = ConfigParser.parse(yaml)
+        config.layout.metadataLabels shouldBe "german"
+        config.layout.metadataPosition shouldBe "bottom"
+    }
+
+    @Test
+    fun `parse config with default metadata settings`() {
+        val yaml = """
+            book:
+              title: "Test"
+        """.trimIndent()
+        val config = ConfigParser.parse(yaml)
+        config.layout.metadataLabels shouldBe "abbreviated"
+        config.layout.metadataPosition shouldBe "top"
+    }
+
     @Test
     fun `parse config ignores unknown properties`() {
         val yaml = """