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>

internal/adapters/outbound/stdout/sink.go

@@ -0,0 +1,58 @@
+package stdout
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"sync"
+
+	"github.com/logcorrelator/logcorrelator/internal/domain"
+)
+
+// Config holds the stdout sink configuration.
+type Config struct {
+	Enabled bool
+}
+
+// StdoutSink writes correlated logs to stdout as JSON lines.
+type StdoutSink struct {
+	config Config
+	mu     sync.Mutex
+	enc    *json.Encoder
+}
+
+// NewStdoutSink creates a new stdout sink.
+func NewStdoutSink(config Config) *StdoutSink {
+	return &StdoutSink{
+		config: config,
+		enc:    json.NewEncoder(os.Stdout),
+	}
+}
+
+// Name returns the sink name.
+func (s *StdoutSink) Name() string {
+	return "stdout"
+}
+
+// Write writes a correlated log to stdout.
+func (s *StdoutSink) Write(ctx context.Context, log domain.CorrelatedLog) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if err := s.enc.Encode(log); err != nil {
+		return fmt.Errorf("failed to write to stdout: %w", err)
+	}
+
+	return nil
+}
+
+// Flush flushes any buffered data (no-op for stdout).
+func (s *StdoutSink) Flush(ctx context.Context) error {
+	return nil
+}
+
+// Close closes the sink (no-op for stdout).
+func (s *StdoutSink) Close() error {
+	return nil
+}