feat(readarr): add a scrollable overview popup to author details

An author's overview renders as the last line of a description box that
does not scroll, so a long overview overflows with no way to read the
rest. Pressing v on the author details Books tab now opens a popup
holding the full overview.

The popup owns its own ScrollableText, built fresh from the author's
overview when it opens and torn down on Esc so a reopened popup starts
at the top. Scrolling mutates only that owned state. The background
paragraph renders the Author record's overview, which carries no scroll
offset, so it cannot scroll along with the popup.

Add a view keybinding bound to v, cite it from the author details
context clues, and give the popup its own clue set so it does not
inherit the hints of the view underneath.

src/app/key_binding.rs

@@ -27,6 +27,7 @@ generate_keybindings! {
   filter,
   sort,
   edit,
+  view,
   logs,
   tasks,
   test,
@@ -142,6 +143,11 @@ pub const DEFAULT_KEYBINDINGS: KeyBindings = KeyBindings {
     alt: None,
     desc: "edit",
   },
+  view: KeyBinding {
+    key: Key::Char('v'),
+    alt: None,
+    desc: "view",
+  },
   events: KeyBinding {
     key: Key::Char('e'),
     alt: None,