Fix build, shutdown cleanup and player data lifecycle

[Rethinger]

The project did not build: de.eisi05:NpcApi-Paper is published on JitPack but
no such repository was declared, so dependency resolution failed outright. The
CI workflow was an unmodified GitHub template that would have failed anyway --
JDK 11 against a Java 21 source level, and an mvn deploy step with no
distributionManagement in the POM.

Build:

• Declare the JitPack repository so NpcApi-Paper resolves.
• CI: JDK 21, build on push and pull_request (not only on release), upload the
  jar as an artifact, and attach it to releases instead of deploying nowhere.
• Pin maven-surefire-plugin 3.2.5. Maven < 3.9 defaults to surefire 2.12.4,
  which cannot run JUnit 5 and reports "no tests to run" instead of failing.
• Relocate the shaded NpcApi classes so the plugin cannot clash with another
  plugin bundling the same library.
• Drop dev.folia:folia-api (zero usages, and pinned to 1.20.1 in a 1.21.1
  project) and the test-scope spigot-api 1.21.3 that conflicted with
  paper-api 1.21.1; paper-api already covers the Bukkit API the tests use.
• Restrict resource filtering to plugin.yml, the only resource using ${}.
• Restore .gitignore, deleted in 5088e94.

Shutdown:

• Add the Cleanable interface and collect registered components into a list
  that onDisable() walks. Bukkit cancels scheduler tasks by itself, but boss
  bars stayed pinned to the screens of players who survived a /reload while
  the summoned boss stayed in the world untracked.
• Stop localising the disable log line: messageManager is null when startup
  failed early, and the NPE masked the original error.

Player data:

• Evict a player's cached profile on quit. DataManager loaded profiles lazily
  and never removed them, so the cache grew for every player who ever joined.
• Back the cache with a ConcurrentHashMap; it is read from scheduler tasks.
• Add saveAsync() for the five-minute autosave: configurations are serialised
  on the main thread, only the disk writes move off it. The old path wrote
  every cached profile plus a backup copy inline on the server tick.

Cleanup:

• Remove src/main/NpcApi-Paper-master/, a vendored copy of the upstream Gradle
  project (47 files, incl. a gradle-wrapper.jar). Maven only compiles
  src/main/java, so it never took part in the build.
• Remove bosses/backup/OriginalBoss2Backup.java; git history covers this.
• Register TextureTestCommand, declared in plugin.yml but never bound.
• Gate Act4Listener behind act4.autoSpawnArtifacts instead of a commented-out
  registration line.
• Fail loudly when a command is missing from plugin.yml rather than NPE.
• Drop the duplicate getNpcManager() getter; keep getNPCManager().
• Replace printStackTrace() with logger calls that keep the stack trace.
• Correct README claims that did not match the code: storage is YAML, not
  JSON, and saving was neither async nor cleaning tasks up until now.

Add PlayerSettingsTest covering the dialog speed cycle and fromString
fallback.

Co-Authored-By: Claude Opus 5 noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_017441xEm5EainbMSewf8u6e