Fix #1: 500 error when creating first book

The 500 error occurred because the create template was missing the
genres, authors, and locations data needed to render the form.

src/hxbooks/main.py

@@ -303,19 +303,21 @@ def create_book() -> ResponseReturnValue:
 
         except DuplicateISBNError as e:
             flash(f"Error: {e}", "error")
-            return render_template("book/create.html.j2", form_data=request.form)
 
         except ValidationError as e:
             _flash_validation_errors(e)
 
-            return render_template("book/create.html.j2", form_data=request.form)
-
         except Exception as e:
             logger.error(f"Error creating book '{form_data.title}': {e}", exc_info=True)
             flash(f"Error creating book: {e}", "error")
-            return render_template("book/create.html.j2", form_data=request.form)
 
-    return render_template("book/create.html.j2")
+    return render_template(
+        "book/create.html.j2",
+        form_data=request.form,
+        genres=library.list_genres(),
+        authors=library.list_authors(),
+        locations=library.list_locations(),
+    )
 
 
 @bp.route("/book/<int:book_id>/edit", methods=["POST"])