v2.3: Major refactoring, Lavalink music system, Spotify support, CI/CD

- Full refactoring: max 200 lines/file, max 3 files/dir, KISS/DRY/SOLID
- Lavalink client 3.4.0 + LavaSrc plugin (Spotify, Apple Music, Deezer)
- 3-bot architecture: main (!), music (q!), radio (r!)
- Filters: bassboost, nightcore, vaporwave, equalizer
- Slash commands for music (/play, /skip, etc.)
- Persistent queue in SQLite, auto-leave timer
- Radio manager with auto-reconnect
- Custom welcome GIF greetings via nekos.life
- JDA 5.6.1, gson 2.14, hikaricp 6.3, all deps updated
- Fixed YouTube playback via ytmsearch (LavaSrc)
- CI/CD: Docker publish + release workflows
- SpotBugs: all real bugs fixed, ignoreFailures=false
- Checkstyle: Google Style (adapted), 0 violations

gradle/libs.versions.toml

@@ -1,24 +1,26 @@
 [versions]
-jda = "5.0.0-beta.20"
-lavaplayer = "2.2.2"
-dotenv = "3.0.0"
-slf4j = "2.0.12"
-logback = "1.5.3"
-gson = "2.10.1"
-caffeine = "3.1.8"
+jda = "5.6.1"
+lavaplayer = "2.2.3"
+lavalinkClient = "3.4.0"
+dotenv = "3.2.0"
+slf4j = "2.1.0-alpha1"
+logback = "1.5.18"
+gson = "2.14.0"
+caffeine = "3.2.0"
 guice = "7.0.0"
-sqlite = "3.45.1.0"
-hikaricp = "5.1.0"
-junit = "5.10.2"
-mockito = "5.11.0"
-junitPlatformLauncher = "1.10.2"
-checkstyle = "10.21.4"
-spotbugs = "6.1.7"
+sqlite = "3.49.1.0"
+hikaricp = "6.3.0"
+junit = "5.12.1"
+mockito = "5.15.2"
+junitPlatformLauncher = "1.12.1"
+checkstyle = "10.23.0"
+spotbugs = "4.9.3"
 spotbugsPlugin = "6.1.7"
 
 [libraries]
 jda = { module = "net.dv8tion:JDA", version.ref = "jda" }
 lavaplayer = { module = "dev.arbjerg:lavaplayer", version.ref = "lavaplayer" }
+lavalink-client = { module = "dev.arbjerg:lavalink-client", version.ref = "lavalinkClient" }
 dotenv = { module = "io.github.cdimascio:dotenv-java", version.ref = "dotenv" }
 slf4j-api = { module = "org.slf4j:slf4j-api", version.ref = "slf4j" }
 logback-classic = { module = "ch.qos.logback:logback-classic", version.ref = "logback" }