feat: support inline images within song pages (Closes #2)

Add {image: path} directive to embed images at any position within a song's
sections. SongLine gains an optional imagePath field; when set, the line
represents an inline image rather than chord/lyric content. The renderer
scales and centers images within the content width. MeasurementEngine
reserves 40mm height per inline image for layout calculations.

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

parser/src/main/kotlin/de/pfadfinder/songbook/parser/ChordProParser.kt

@@ -129,6 +129,13 @@ object ChordProParser {
                     "end_of_repeat", "eor" -> {
                         flushSection()
                     }
+                    "image" -> if (value != null) {
+                        // Inline image within a song section
+                        if (currentType == null) {
+                            currentType = SectionType.VERSE
+                        }
+                        currentLines.add(SongLine(imagePath = value.trim()))
+                    }
                     "start_of_notes", "son" -> {
                         inNotesBlock = true
                     }

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

@@ -577,4 +577,55 @@ class ChordProParserTest {
         song.notes[1] shouldBe "Paragraph two."
         song.notes[2] shouldBe "Paragraph three."
     }
+
+    @Test
+    fun `parse image directive within song section`() {
+        val input = """
+            {title: Song}
+            {start_of_verse}
+            [Am]Hello world
+            {image: images/drawing.png}
+            [C]Goodbye world
+            {end_of_verse}
+        """.trimIndent()
+        val song = ChordProParser.parse(input)
+        song.sections shouldHaveSize 1
+        song.sections[0].lines shouldHaveSize 3
+        song.sections[0].lines[0].segments[0].chord shouldBe "Am"
+        song.sections[0].lines[1].imagePath shouldBe "images/drawing.png"
+        song.sections[0].lines[1].segments.shouldBeEmpty()
+        song.sections[0].lines[2].segments[0].chord shouldBe "C"
+    }
+
+    @Test
+    fun `parse image directive outside section creates implicit verse`() {
+        val input = """
+            {title: Song}
+            {image: images/landscape.jpg}
+        """.trimIndent()
+        val song = ChordProParser.parse(input)
+        song.sections shouldHaveSize 1
+        song.sections[0].type shouldBe SectionType.VERSE
+        song.sections[0].lines shouldHaveSize 1
+        song.sections[0].lines[0].imagePath shouldBe "images/landscape.jpg"
+    }
+
+    @Test
+    fun `parse multiple image directives`() {
+        val input = """
+            {title: Song}
+            {start_of_verse}
+            {image: img1.png}
+            Some text
+            {image: img2.png}
+            {end_of_verse}
+        """.trimIndent()
+        val song = ChordProParser.parse(input)
+        song.sections[0].lines shouldHaveSize 3
+        song.sections[0].lines[0].imagePath shouldBe "img1.png"
+        song.sections[0].lines[0].segments.shouldBeEmpty()
+        song.sections[0].lines[1].imagePath.shouldBeNull()
+        song.sections[0].lines[1].segments[0].text shouldBe "Some text"
+        song.sections[0].lines[2].imagePath shouldBe "img2.png"
+    }
 }