feat: add main entry point and stdout sink for Docker build

- Create cmd/logcorrelator/main.go as the application entry point
  - Loads configuration from YAML file
  - Initializes Unix socket sources, file/ClickHouse/stdout sinks
  - Sets up correlation service and orchestrator
  - Handles graceful shutdown on SIGINT/SIGTERM
  - Supports -version flag to print version

- Add internal/adapters/outbound/stdout/sink.go
  - Implements CorrelatedLogSink interface for stdout output
  - Writes JSON lines to standard output

- Fix .gitignore to use /logcorrelator instead of logcorrelator
  - Prevents cmd/logcorrelator directory from being ignored

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

.gitignore

@@ -8,7 +8,7 @@
 *.dll
 *.so
 *.dylib
-logcorrelator
+/logcorrelator
 
 # Test binary
 *.test