feat: anchor footer elements to bottom of page (Closes #31)

Footer elements (notes, Worte/Weise metadata, reference book table) on song pages now render at fixed positions anchored to the bottom margin instead of flowing after song content. This ensures consistent vertical positioning across all pages regardless of content length.

renderer-pdf/src/main/kotlin/de/pfadfinder/songbook/renderer/pdf/PdfBookRenderer.kt

@@ -424,60 +424,68 @@ class PdfBookRenderer : BookRenderer {
             y -= config.layout.verseSpacing / 0.3528f
         }
 
-        // Render notes on the last page
-        if (isLastPage && song.notes.isNotEmpty()) {
-            y -= 4f
+        // Render footer elements (notes, metadata, references) anchored to the bottom of the page.
+        // Instead of flowing from the current y position after song content, we compute a fixed
+        // starting Y at the top of the footer area (bottomMargin + footerReservation) and render
+        // top-down: notes -> metadata -> references. This ensures footer elements always appear
+        // at the same vertical position regardless of how much song content is on the page.
+        if (isLastPage && footerReservation > 0f) {
             val metaFont = fontMetrics.getBaseFont(config.fonts.metadata)
             val metaSize = config.fonts.metadata.size
-            val noteLineHeight = metaSize * 1.5f
 
-            for ((idx, note) in song.notes.withIndex()) {
-                val wrappedLines = wrapText(note, metaFont, metaSize, contentWidth)
-                for (wrappedLine in wrappedLines) {
-                    cb.beginText()
-                    cb.setFontAndSize(metaFont, metaSize)
-                    cb.setColorFill(Color.GRAY)
-                    cb.setTextMatrix(leftMargin, y - metaSize)
-                    cb.showText(wrappedLine)
-                    cb.endText()
-                    y -= noteLineHeight
-                }
-                // Add paragraph spacing between note paragraphs
-                if (idx < song.notes.size - 1) {
-                    y -= noteLineHeight * 0.3f
-                }
-            }
-        }
+            // The footer area spans from bottomMargin to bottomMargin + footerReservation.
+            // Start rendering from the top of this area, flowing downward.
+            var footerY = bottomMargin + footerReservation
 
-        // Render metadata at bottom of song page (if configured) - on the last page only
-        if (renderMetaAtBottom && isLastPage) {
-            val metaParts = buildMetadataLines(song, config)
-            if (metaParts.isNotEmpty()) {
-                y -= 4f
-                val metaFont = fontMetrics.getBaseFont(config.fonts.metadata)
-                val metaSize = config.fonts.metadata.size
-                for (metaLine in metaParts) {
-                    val wrappedLines = wrapText(metaLine, metaFont, metaSize, contentWidth)
+            // Render notes (topmost footer element)
+            if (song.notes.isNotEmpty()) {
+                footerY -= 4f  // gap before notes
+                val noteLineHeight = metaSize * 1.5f
+                for ((idx, note) in song.notes.withIndex()) {
+                    val wrappedLines = wrapText(note, metaFont, metaSize, contentWidth)
                     for (wrappedLine in wrappedLines) {
                         cb.beginText()
                         cb.setFontAndSize(metaFont, metaSize)
                         cb.setColorFill(Color.GRAY)
-                        cb.setTextMatrix(leftMargin, y - metaSize)
+                        cb.setTextMatrix(leftMargin, footerY - metaSize)
                         cb.showText(wrappedLine)
                         cb.endText()
-                        y -= metaSize * 1.5f
+                        footerY -= noteLineHeight
+                    }
+                    if (idx < song.notes.size - 1) {
+                        footerY -= noteLineHeight * 0.3f
                     }
                 }
             }
-        }
 
-        // Render reference book footer on the last page of the song
-        if (config.referenceBooks.isNotEmpty() && song.references.isNotEmpty() && isLastPage) {
-            y -= 4f  // gap before reference footer
-            renderReferenceFooter(
-                cb, fontMetrics, config, song,
-                leftMargin, y, contentWidth
-            )
+            // Render metadata (Worte/Weise) below notes, if configured at bottom
+            if (renderMetaAtBottom) {
+                val metaParts = buildMetadataLines(song, config)
+                if (metaParts.isNotEmpty()) {
+                    footerY -= 4f  // gap before metadata
+                    for (metaLine in metaParts) {
+                        val wrappedLines = wrapText(metaLine, metaFont, metaSize, contentWidth)
+                        for (wrappedLine in wrappedLines) {
+                            cb.beginText()
+                            cb.setFontAndSize(metaFont, metaSize)
+                            cb.setColorFill(Color.GRAY)
+                            cb.setTextMatrix(leftMargin, footerY - metaSize)
+                            cb.showText(wrappedLine)
+                            cb.endText()
+                            footerY -= metaSize * 1.5f
+                        }
+                    }
+                }
+            }
+
+            // Render reference book footer (bottommost footer element, just above page number)
+            if (config.referenceBooks.isNotEmpty() && song.references.isNotEmpty()) {
+                footerY -= 4f  // gap before reference footer
+                renderReferenceFooter(
+                    cb, fontMetrics, config, song,
+                    leftMargin, footerY, contentWidth
+                )
+            }
         }
     }