Set up book project: Markdown→CSS→PDF pipeline for KDP

Adds the full authoring and build toolchain for "Das Kaleidoskop der
Schlummerwelten" — all 12 story content files in Markdown, Nunjucks
HTML templates, CSS print layout, and Puppeteer-based PDF generation
targeting Amazon KDP (8.5×8.5 in, 0.125in bleed).

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

styles/print.css

@@ -0,0 +1,34 @@
+/* KDP: 8.5×8.5 in trim, 0.125in bleed on all sides */
+@page {
+  size: 8.75in 8.75in;
+  margin: 0;
+}
+
+* {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+html, body {
+  width: 8.75in;
+  background: white;
+}
+
+.page {
+  width: 8.75in;
+  height: 8.75in;
+  position: relative;
+  overflow: hidden;
+  page-break-after: always;
+  break-after: page;
+}
+
+/* Safe zone: content that must not be cut stays 0.25in from bleed edge */
+.page--text .text-page-inner,
+.page--title .title-content,
+.page--toc,
+.page--imprint .imprint-content {
+  /* 0.125in bleed + 0.25in safety margin = 0.375in from PDF edge */
+  padding: 0.75in;
+}