feat(readarr): render the edition details popup

Draw the edition details popup over the book details view. The popup body is
the scrollable text the book details handler builds from the already loaded
edition row, so it needs no tabs and no network call.

The text styling is extracted into a named function so both branches are unit
tested, and the shared test fixture now holds the real field lines instead of a
placeholder, which exercises the scroll offset and the values that themselves
contain a colon.

src/models/servarr_data/readarr/readarr_data.rs

@@ -447,7 +447,20 @@ impl ReadarrData<'_> {
       .set_items(vec!["Standard".to_owned()]);
 
     let edition_details_modal = EditionDetailsModal {
-      edition_details: ScrollableText::with_string("Some details".to_owned()),
+      edition_details: ScrollableText::with_string(
+        "Title: Test Edition
+Format: Hardcover
+Language: English
+Publisher: DAW Books
+Page Count: 288
+Release Date: 2023-05-20 00:00:00 UTC
+ISBN13: 9780756404079
+ASIN: B0043RSJ9S
+Ratings: 4.5 (1000 votes)
+Monitored: true
+Overview: A test edition overview."
+          .to_owned(),
+      ),
     };
 
     let mut book_details_modal = BookDetailsModal {