Extract and insert 97 images from reference PDF into songs

Extract images from the CL6 PDF using pdfimages, map them to songs
via page-to-CL number matching, and insert \songimage commands.
Add insert-images.py script for repeatable extraction.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

songs/es-soll-sich-der-mensch.tex

@@ -57,4 +57,6 @@ Da fing das Theater von vorne an; / \\
 man gewöhnt sich daran! Tüterütütütü
 \end{verse}
 
+\songimage{images/img-054.png}
+
 \end{song}