Add Docker support and environment configuration

Introduced Dockerfile, .dockerignore, and example environment file for containerization. Added compose.yml for Docker Compose setup and renamed docker-compose.dev.yml to compose.dev.yml. Updated build.gradle.kts for Java 21 and shadow plugin, and improved .gitignore and .gitattributes. Refactored Config.java to reorder ENV initialization.

docker-compose.dev.yml

@@ -1,16 +0,0 @@
-services:
-  couchbase:
-    image: couchbase:community-7.6.2
-    ports:
-      - "8091-8097:8091-8097"
-      - "9123:9123"
-      - "11207:11207"
-      - "11210:11210"
-      - "11280:11280"
-      - "18091-18097:18091-18097"
-    volumes:
-      - couchbase_data:/opt/couchbase/var
-    restart: unless-stopped
-
-volumes:
-  couchbase_data: