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/java/com/github/damontecres/wholphin/util/BlockingList.kt

@@ -2,6 +2,7 @@ package com.github.damontecres.wholphin.util
 
 import java.util.function.IntFunction
 import java.util.function.Predicate
+import kotlin.random.Random
 
 /**
  * A [List] which has function that will wait for a result
@@ -17,6 +18,11 @@ interface BlockingList<T> : List<T> {
      */
     suspend fun indexOfBlocking(predicate: Predicate<T>): Int
 
+    suspend fun randomBlocking(): T {
+        val index = Random.nextInt(size)
+        return getBlocking(index)
+    }
+
     companion object {
         /**
          * Create a [BlockingList] over a regular [List]