feat: add support for foreword/preface pages (Closes #1)

Add ForewordConfig to BookConfig, Foreword model type, ForewordParser for
text files (quote/paragraphs/signatures), ForewordPage in PageContent,
pipeline integration to insert foreword after TOC, and PDF rendering with
styled quote, horizontal rule separator, word-wrapped paragraphs, and
right-aligned signatures.

Also adds Gradle wrapper and adjusts build toolchain for JDK 25 compat.

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

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

@@ -0,0 +1,96 @@
+package de.pfadfinder.songbook.parser
+
+import de.pfadfinder.songbook.model.Foreword
+import java.io.File
+
+object ForewordParser {
+
+    /**
+     * Parses a foreword text file into a [Foreword] object.
+     *
+     * Format:
+     * - Lines starting with `> ` are collected as the quote (multiple lines joined)
+     * - `---` is a horizontal rule separator (marks end of quote section)
+     * - Lines starting with `-- ` are signatures
+     * - Other non-blank lines are body text; blank lines separate paragraphs
+     */
+    fun parse(input: String): Foreword {
+        val lines = input.lines()
+
+        val quoteLines = mutableListOf<String>()
+        val signatures = mutableListOf<String>()
+        val paragraphs = mutableListOf<String>()
+
+        var currentParagraph = StringBuilder()
+        var inQuote = true  // Start assuming we might be in the quote section
+        var foundSeparator = false
+
+        for (rawLine in lines) {
+            val line = rawLine.trimEnd()
+
+            // Quote lines (before separator)
+            if (!foundSeparator && line.trimStart().startsWith("> ")) {
+                quoteLines.add(line.trimStart().removePrefix("> "))
+                continue
+            }
+
+            // If we had quote lines but now see non-quote content before separator,
+            // the quote section is done
+            if (!foundSeparator && quoteLines.isNotEmpty() && line.trimStart().isNotEmpty() && !line.trimStart().startsWith("> ")) {
+                if (line.trim() == "---") {
+                    foundSeparator = true
+                    inQuote = false
+                    continue
+                }
+            }
+
+            // Separator line
+            if (line.trim() == "---") {
+                foundSeparator = true
+                inQuote = false
+                continue
+            }
+
+            // Signature lines
+            if (line.trimStart().startsWith("-- ")) {
+                signatures.add(line.trimStart().removePrefix("-- "))
+                continue
+            }
+
+            // Skip quote processing after we established there are no quotes
+            if (inQuote && quoteLines.isEmpty() && line.isBlank()) {
+                continue
+            }
+
+            inQuote = false
+
+            // Body paragraphs
+            if (line.isBlank()) {
+                if (currentParagraph.isNotEmpty()) {
+                    paragraphs.add(currentParagraph.toString().trim())
+                    currentParagraph = StringBuilder()
+                }
+            } else {
+                if (currentParagraph.isNotEmpty()) {
+                    currentParagraph.append(" ")
+                }
+                currentParagraph.append(line.trim())
+            }
+        }
+
+        // Flush remaining paragraph
+        if (currentParagraph.isNotEmpty()) {
+            paragraphs.add(currentParagraph.toString().trim())
+        }
+
+        val quote = if (quoteLines.isNotEmpty()) quoteLines.joinToString(" ") else null
+
+        return Foreword(
+            quote = quote,
+            paragraphs = paragraphs,
+            signatures = signatures
+        )
+    }
+
+    fun parseFile(file: File): Foreword = parse(file.readText())
+}

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

@@ -1,6 +1,8 @@
 package de.pfadfinder.songbook.parser
 
 import io.kotest.matchers.collections.shouldHaveSize
+import io.kotest.matchers.nulls.shouldBeNull
+import io.kotest.matchers.nulls.shouldNotBeNull
 import io.kotest.matchers.shouldBe
 import kotlin.test.Test
 
@@ -167,6 +169,29 @@ class ConfigParserTest {
         config.layout.verseSpacing shouldBe 6f
     }
 
+    @Test
+    fun `parse config with foreword section`() {
+        val yaml = """
+            book:
+              title: "Test"
+            foreword:
+              file: "./vorwort.txt"
+        """.trimIndent()
+        val config = ConfigParser.parse(yaml)
+        config.foreword.shouldNotBeNull()
+        config.foreword!!.file shouldBe "./vorwort.txt"
+    }
+
+    @Test
+    fun `parse config without foreword section has null foreword`() {
+        val yaml = """
+            book:
+              title: "Test"
+        """.trimIndent()
+        val config = ConfigParser.parse(yaml)
+        config.foreword.shouldBeNull()
+    }
+
     @Test
     fun `parse config ignores unknown properties`() {
         val yaml = """

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

@@ -0,0 +1,150 @@
+package de.pfadfinder.songbook.parser
+
+import io.kotest.matchers.collections.shouldBeEmpty
+import io.kotest.matchers.collections.shouldHaveSize
+import io.kotest.matchers.nulls.shouldBeNull
+import io.kotest.matchers.nulls.shouldNotBeNull
+import io.kotest.matchers.shouldBe
+import kotlin.test.Test
+
+class ForewordParserTest {
+
+    @Test
+    fun `parse foreword with quote, paragraphs and signatures`() {
+        val input = """
+            > This is a quote line one
+            > and quote line two
+            ---
+            This is the first paragraph of the foreword body.
+            It continues on the next line.
+
+            This is the second paragraph.
+
+            -- Max Mustermann
+            -- Erika Mustermann
+        """.trimIndent()
+
+        val foreword = ForewordParser.parse(input)
+
+        foreword.quote.shouldNotBeNull()
+        foreword.quote shouldBe "This is a quote line one and quote line two"
+        foreword.paragraphs shouldHaveSize 2
+        foreword.paragraphs[0] shouldBe "This is the first paragraph of the foreword body. It continues on the next line."
+        foreword.paragraphs[1] shouldBe "This is the second paragraph."
+        foreword.signatures shouldHaveSize 2
+        foreword.signatures[0] shouldBe "Max Mustermann"
+        foreword.signatures[1] shouldBe "Erika Mustermann"
+    }
+
+    @Test
+    fun `parse foreword without quote`() {
+        val input = """
+            This is just a paragraph.
+
+            And another one.
+
+            -- Author Name
+        """.trimIndent()
+
+        val foreword = ForewordParser.parse(input)
+
+        foreword.quote.shouldBeNull()
+        foreword.paragraphs shouldHaveSize 2
+        foreword.paragraphs[0] shouldBe "This is just a paragraph."
+        foreword.paragraphs[1] shouldBe "And another one."
+        foreword.signatures shouldHaveSize 1
+        foreword.signatures[0] shouldBe "Author Name"
+    }
+
+    @Test
+    fun `parse foreword without signatures`() {
+        val input = """
+            > A beautiful quote
+            ---
+            The foreword body text goes here.
+        """.trimIndent()
+
+        val foreword = ForewordParser.parse(input)
+
+        foreword.quote shouldBe "A beautiful quote"
+        foreword.paragraphs shouldHaveSize 1
+        foreword.paragraphs[0] shouldBe "The foreword body text goes here."
+        foreword.signatures.shouldBeEmpty()
+    }
+
+    @Test
+    fun `parse empty foreword`() {
+        val foreword = ForewordParser.parse("")
+
+        foreword.quote.shouldBeNull()
+        foreword.paragraphs.shouldBeEmpty()
+        foreword.signatures.shouldBeEmpty()
+    }
+
+    @Test
+    fun `parse foreword with only paragraphs`() {
+        val input = """
+            First paragraph.
+
+            Second paragraph.
+
+            Third paragraph.
+        """.trimIndent()
+
+        val foreword = ForewordParser.parse(input)
+
+        foreword.quote.shouldBeNull()
+        foreword.paragraphs shouldHaveSize 3
+        foreword.paragraphs[0] shouldBe "First paragraph."
+        foreword.paragraphs[1] shouldBe "Second paragraph."
+        foreword.paragraphs[2] shouldBe "Third paragraph."
+        foreword.signatures.shouldBeEmpty()
+    }
+
+    @Test
+    fun `parse foreword with multi-line paragraph`() {
+        val input = """
+            This is a long paragraph that
+            spans multiple lines and should
+            be joined into a single paragraph.
+        """.trimIndent()
+
+        val foreword = ForewordParser.parse(input)
+
+        foreword.paragraphs shouldHaveSize 1
+        foreword.paragraphs[0] shouldBe "This is a long paragraph that spans multiple lines and should be joined into a single paragraph."
+    }
+
+    @Test
+    fun `parse foreword with only a quote`() {
+        val input = """
+            > Just a quote
+            ---
+        """.trimIndent()
+
+        val foreword = ForewordParser.parse(input)
+
+        foreword.quote shouldBe "Just a quote"
+        foreword.paragraphs.shouldBeEmpty()
+        foreword.signatures.shouldBeEmpty()
+    }
+
+    @Test
+    fun `parse foreword with multiple signatures`() {
+        val input = """
+            Some text here.
+
+            -- Person One
+            -- Person Two
+            -- Person Three
+        """.trimIndent()
+
+        val foreword = ForewordParser.parse(input)
+
+        foreword.paragraphs shouldHaveSize 1
+        foreword.signatures shouldHaveSize 3
+        foreword.signatures[0] shouldBe "Person One"
+        foreword.signatures[1] shouldBe "Person Two"
+        foreword.signatures[2] shouldBe "Person Three"
+    }
+}