feat(M1): Fabric scaffold for MC 1.21.6 with /videoStick

- video_player mod id, 영상재생모드 display name
- VideoAnchorBlock + VideoAnchorBlockEntity (placeholder)
- VideoStickItem
- /videoStick (+ /videostick alias) command gives the stick
- gradle 9.5.1 wrapper, fabric-loom 1.16.2, Java 21 toolchain
- works in both singleplayer and dedicated server (environment: *)

.gitignore

@@ -0,0 +1,8 @@
+.gradle/
+build/
+out/
+.idea/
+.vscode/
+*.iml
+.fabric/
+run/