#1714 Add support for edge and spine INTERIORART

[Ahasuerus]

Add support for art that appears on publications' edges. [[Template:PubContentFields:Page]] currently doesn't specify how to handle this type of cases (see https://en.wikipedia.org/wiki/Fore-edge_painting for real-life examples.) As per Rules & Standards consensus, we want to update the software and [[Template:PubContentFields:Page]] to add support for the following types of specially designated "page numbers" for INTERIORART:

• edge - design or artwork printed, stenciled, or sprayed onto the trimmed page edges of the book. In cases where different art is found on each edge, use the following:
  te - top edge
  fe - fore-edge or facing edge
  **be - bottom edge
• sp - art that appears only on the spine of the book. Do not use if the spine art is simply a continuation of the rest of the cover art (front and/or back).

[Ahasuerus]

Implemented in:

common/isfdb.py
common/library.py

Installed in SVN 1307 on 2026-04-06. Closing the FR.