refactor: KISS/DRY/SOLID раунд + багфиксы радио/voice/message

Что сделано:
- RatingService (getDeterministicValue + cooldown — одна точка)
- ModerationHelper (trunc/err — одна точка)
- VoiceHelper (waitForCondition с таймаутом)
- SocialCommand (7 файлов → 1 Flavor enum)
- SwapCommand + CaseLookupCommand (Split SRP)
- PlayCommand 219→150, BotInitializer 182→135, RankCardGenerator (1→4)
- MetricsCollector 182→143, TrackScheduler 202→146, VoiceChannelManager 187→150
- QueueCommands 207→149, VoiceSetupPrefixCommand 183→146, ServerStatsService 187→150
- GuildMusicManager 167→150, SqlEconomyRepository 169→149, GenerateRatingsCommand 172→147
- RadioManager: таймауты, volume при старте, защита от утечки
- VoiceTracker: race condition fix + LevelUpNotifier
- MessageCooldownService: in-memory cache
- MessageListener: LevelUpNotifier вместо inline embed
- ResetLevelsButtonHandler: правильный парсинг кнопки
- OkHttp: java.net.http → OkHttp 5.4.0
- SlowmodeCommandTest: SelfMember fix
Всё: 415 tests, 2 pre-existing, checkstyle чисто

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