Fix suggestions mixing content from different libraries and update recommendation logic (#644)

## Description
This PR aims to fix #638 where the "Suggestions" row was mixing up
content from different libraries that shared the same library type. For
example you were in the Anime library, you'd see regular TV shows
showing up, as the TV Shows and Anime libraries would both be "Show"
libraries.

As @damontecres mentioned in the issue discussion, the
`/Items/Suggestions` endpoint Wholphin is using just returns random
items from the same library type, with no special logic or
recommendation algorithm.

I also looked at how the official WebUI handles this. It basically just
mixes "Resume," "Next Up," and "Latest Items" together. That felt a bit
redundant since we usually have dedicated rows for those things anyway;
I wanted to try something that helps discover new content.

I replaced the broken endpoint with a few custom `GetItemsRequest`
calls. These work correctly with the `ParentId` filter, so we only get
results from the library we are actually looking at. Additionally, I
added in some logic that takes into account what the user has been
watching to tailor the suggestions a little bit.

The new logic uses a 40/30/30 mix (this can of course be tweaked as
needed)

- Tailored (40%): Grabs your recently watched items from this library,
checks their genres, and returns items from the same genre.

- Random (30%): Random unwatched stuff from this library.

- New (30%): Recently added items.

This is implemented using only `GetItemsRequest` API calls using
filters, rather than any specialized endpoints like the
`/Items/Suggestions` endpoint. This means the feature should be
predictable and stable. If Jellyfin ever adds an actual recommendation
algorithm and endpoint to call it, I imagine we would want to switch to
that in the future though.

I also added some failsafe logic to make sure there will be diversity in
the "recently watched" items that get pulled, in case a user might have
recently binged a TV show. We wouldn't want every single recommendation
to be based off of that one show.

To fix this, I changed the query to fetch the last 20 history items
instead of just the top 3. Then, we filter that list client-side to find
unique Series IDs. If the user watched 10 episodes of One Piece in a
row, the logic collapses them into a single "One Piece" entry and moves
on to the next distinct show they watched. This guarantees we get
variety in the source material for recommendations.

This is a work in progress right now, mainly due to performance. For my
server it takes about 10-15 seconds to load the Suggestions row when I
tested. This is unacceptable in my opinion, especially if we ever intend
to add a Suggestions row like this to the home page like Plex does. I
have some ideas on how to improve performance, but I'm open to
suggestions.

### Related issues
Resolves #638 

### Screenshots

Before:

<img width="1953" height="1162" alt="suggestions1"
src="https://github.com/user-attachments/assets/6e301c67-1a46-46b5-8184-3adb9e52b330"
/>


After:

<img width="1937" height="1108" alt="suggestions3"
src="https://github.com/user-attachments/assets/b9563865-4055-40b6-b452-f94c26c8b6e9"
/>


### AI/LLM usage
I used Claude Code to help write the Kotlin Coroutines so the API calls
run at the same time. I also used it to write the tests in
`TestSuggestionsLogic.kt`.

---------

Co-authored-by: Damontecres <damontecres@gmail.com>

app/src/main/java/com/github/damontecres/wholphin/MainActivity.kt

@@ -52,6 +52,7 @@ import com.github.damontecres.wholphin.services.RefreshRateService
 import com.github.damontecres.wholphin.services.ServerEventListener
 import com.github.damontecres.wholphin.services.SetupDestination
 import com.github.damontecres.wholphin.services.SetupNavigationManager
+import com.github.damontecres.wholphin.services.SuggestionsSchedulerService
 import com.github.damontecres.wholphin.services.UpdateChecker
 import com.github.damontecres.wholphin.services.UserSwitchListener
 import com.github.damontecres.wholphin.services.hilt.AuthOkHttpClient
@@ -119,6 +120,9 @@ class MainActivity : AppCompatActivity() {
     @Inject
     lateinit var tvProviderSchedulerService: TvProviderSchedulerService
 
+    @Inject
+    lateinit var suggestionsSchedulerService: SuggestionsSchedulerService
+
     // Note: unused but injected to ensure it is created
     @Inject
     lateinit var serverEventListener: ServerEventListener