Add button to navigate to random item (#1916)

## Description
Adds a random button on library tab/grid pages which navigates to a
random item in the list. This goes to the item's detail page.

The random item is chosen with the filters applied. So you could filter
by unplayed Action movies with 7+ stars and the random button will
select from those movies.

Pressing back restores focus on the random button so it's easy to
quickly retry.

### Related issues
Closes #838

### Testing
Emulator

## Screenshots
<img width="935" height="105" alt="image"
src="https://github.com/user-attachments/assets/170b495c-b47d-41ce-93b5-99831f2064c7"
/>
<img width="936" height="114" alt="image"
src="https://github.com/user-attachments/assets/3efa6a11-ebe8-42d7-b023-354b1e6eda37"
/>



## AI or LLM usage
None

app/src/main/res/values/fa_strings.xml

@@ -1,5 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
+    <!-- Names should be prefixed with 'fa_' and use the icon name from FontAwesome -->
+    <!-- Uses v6 of FontAwesome: https://fontawesome.com/v6/icons/classic/solid/<name> -->
+    <!-- Value is '&#x' then the unicode value, then semicolon -->
     <string name="fa_tag" translatable="false">&#xf02b;</string>
     <string name="fa_user" translatable="false">&#xf007;</string>
     <string name="fa_location_dot" translatable="false">&#xf3c5;</string>
@@ -57,4 +60,5 @@
     <string name="fa_repeat" translatable="false">&#xf363;</string>
     <string name="fa_compact_disc" translatable="false">&#xf51f;</string>
     <string name="fa_xmark" translatable="false">&#xf00d;</string>
+    <string name="fa_dice" translatable="false">&#xf522;</string>
 </resources>