Default AnimeSeasonSearchFallback to Always

The FullSeasonNotAired default skipped per-episode fallback for
completed seasons that returned no approved pack. On usenet, completed
seasons frequently exist as individual episodes without a season pack
ever being posted, so the default left those users strictly worse off
than the current main behavior.

The timeout fix this PR is trying to solve comes from the early-exit
on a successful season query, not from suppressing the fallback. When
the season query returns approved results we stop regardless of the
enum value, which is where the vast majority of the per-episode storm
was happening. The fallback branch only runs when no pack exists on
any configured indexer, and in that case firing per-episode is the
only way to find anything.

The enum is kept so torrent-only users who specifically want to cap
worst-case query count can set it to FullSeasonNotAired or Never, but
the out-of-box behavior now matches what fryfrog pointed out on
Discord as the correct expectation.

src/NzbDrone.Core/Configuration/ConfigService.cs

@@ -132,7 +132,7 @@ public int MinimumAge
 
         public AnimeSeasonSearchFallback AnimeSeasonSearchFallback
         {
-            get { return GetValueEnum("AnimeSeasonSearchFallback", AnimeSeasonSearchFallback.FullSeasonNotAired); }
+            get { return GetValueEnum("AnimeSeasonSearchFallback", AnimeSeasonSearchFallback.Always); }
 
             set { SetValue("AnimeSeasonSearchFallback", value); }
         }