feat: split the edition out of a book's title

"Fluent Python, 2nd Edition" is one book with a field for the edition. Left in
the title it also splits the library, since the second edition never looks like
the first. Only a numbered statement is moved, so "Catch 22" keeps its number
and "Global Edition" — which has nowhere to go in an integer column — stays put.

backend/tests/integration/test_book.py

@@ -37,7 +37,8 @@ from pathlib import Path
         (
             Path("tests/data_files/Calculus Made Easy - Silvanus Thompson.pdf"),
             2,
-            "The Project Gutenberg eBook #33283: Calculus Made Easy, 2nd Edition",
+            # The ", 2nd Edition" is split off into `edition`, not kept in the title.
+            "The Project Gutenberg eBook #33283: Calculus Made Easy",
             ["Silvanus Phillips Thompson"],
         ),
     ],