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>

layout/src/main/kotlin/de/pfadfinder/songbook/layout/MeasurementEngine.kt

@@ -15,9 +15,16 @@ class MeasurementEngine(
         // Title height
         heightMm += fontMetrics.measureLineHeight(config.fonts.title, config.fonts.title.size) * 1.5f
 
-        // Metadata line (composer/lyricist)
+        // Metadata lines (composer/lyricist) - may be 1 or 2 lines depending on label style
         if (song.composer != null || song.lyricist != null) {
-            heightMm += fontMetrics.measureLineHeight(config.fonts.metadata, config.fonts.metadata.size) * 1.8f
+            val metaLineHeight = fontMetrics.measureLineHeight(config.fonts.metadata, config.fonts.metadata.size) * 1.8f
+            val useGerman = config.layout.metadataLabels == "german"
+            if (useGerman && song.lyricist != null && song.composer != null && song.lyricist != song.composer) {
+                // Two separate lines: "Worte: ..." and "Weise: ..."
+                heightMm += metaLineHeight * 2
+            } else {
+                heightMm += metaLineHeight
+            }
         }
 
         // Key/capo line