Fix stable scores importing with a LegacyOnlineID of 0

Closes https://github.com/ppy/osu/issues/33435.

The root cause of the issue is that the user's database contained a
whole lot of scores with `LegacyOnlineID` of 0, which would trip up

	https://github.com/ppy/osu/blob/97e6187f0d7c3dbee896596a623e34627135bf0e/osu.Game/Extensions/ModelExtensions.cs#L128-L129

as that method would thus consider scores that are not the same as the
same because of the zero, which later trips up

	https://github.com/ppy/osu/blob/97e6187f0d7c3dbee896596a623e34627135bf0e/osu.Game/Screens/Ranking/SoloResultsScreen.cs#L79

which ends up inserting `Score` into the list several times, which
causes the crash.

You might remember that I tried to fix this once before in
https://github.com/ppy/osu/pull/24794. What I did not realise, however,
is that stable *can still produce replays* that have an online ID of
zero in them, because zero *is just `default(long)`*:

	https://github.com/peppy/osu-stable-reference/blob/7205341bb70000a87fa1bd54e7642772e2af85d7/osu!/GameplayElements/Scoring/Score.cs#L123
	https://github.com/peppy/osu-stable-reference/blob/7205341bb70000a87fa1bd54e7642772e2af85d7/osu!/GameplayElements/Scoring/Score.cs#L350

The alternative way of fixing this would be just to change
`MatchesOnlineID` to reject zeroes, but I think this is a saner overall
direction.

osu.Game/Database/RealmAccess.cs

@@ -98,8 +98,9 @@ namespace osu.Game.Database
         /// 46   2024-12-26    Change beat snap divisor bindings to match stable directionality ¯\_(ツ)_/¯.
         /// 47   2025-01-21    Remove right mouse button binding for absolute scroll. Never use mouse buttons (or scroll) for global actions.
         /// 48   2025-03-19    Clear online status for all qualified beatmaps (some were stuck in a qualified state due to local caching issues).
+        /// 49   2025-06-10    Reset the LegacyOnlineID to -1 for all scores that have it set to 0 (which is semantically the same) for consistency of handling with OnlineID.
         /// </summary>
-        private const int schema_version = 48;
+        private const int schema_version = 49;
 
         /// <summary>
         /// Lock object which is held during <see cref="BlockAllOperations"/> sections, blocking realm retrieval during blocking periods.
@@ -1255,6 +1256,12 @@ namespace osu.Game.Database
                     foreach (var beatmap in beatmaps)
                         beatmap.ResetOnlineInfo(resetOnlineId: false);
                     break;
+
+                case 49:
+                    foreach (var score in migration.NewRealm.All<ScoreInfo>().Where(s => s.LegacyOnlineID == 0))
+                        score.LegacyOnlineID = -1;
+
+                    break;
             }
 
             Logger.Log($"Migration completed in {stopwatch.ElapsedMilliseconds}ms");

osu.Game/Scoring/Legacy/LegacyScoreDecoder.cs

@@ -110,6 +110,9 @@ namespace osu.Game.Scoring.Legacy
                 else if (version >= 20121008)
                     scoreInfo.LegacyOnlineID = sr.ReadInt32();
 
+                if (scoreInfo.LegacyOnlineID == 0)
+                    scoreInfo.LegacyOnlineID = -1;
+
                 byte[] compressedScoreInfo = null;
 
                 if (version >= 30000001)