WIP: Extract daemon runtime into internal/daemonrunner

- Created config.go with Config struct
- Created daemon.go with Daemon struct and Start/Stop methods
- Created logger.go for logging setup
- Created process.go for lock/PID management
- Created fingerprint.go for database validation
- Created flock_unix.go/flock_windows.go for platform-specific locking
- Created git.go for git operations

Still TODO:
- Implement runGlobalDaemon, startRPCServer, runSyncLoop
- Create sync.go, rpc.go, jsonl.go, validation.go
- Update cmd/bd/daemon.go to use daemonrunner

Part of bd-5f26

internal/daemonrunner/logger.go

@@ -0,0 +1,59 @@
+package daemonrunner
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+
+	"gopkg.in/natefinch/lumberjack.v2"
+)
+
+type logger struct {
+	logFunc func(string, ...interface{})
+}
+
+func (l *logger) log(format string, args ...interface{}) {
+	l.logFunc(format, args...)
+}
+
+func (d *Daemon) setupLogger() (*lumberjack.Logger, *logger) {
+	maxSizeMB := getEnvInt("BEADS_DAEMON_LOG_MAX_SIZE", 10)
+	maxBackups := getEnvInt("BEADS_DAEMON_LOG_MAX_BACKUPS", 3)
+	maxAgeDays := getEnvInt("BEADS_DAEMON_LOG_MAX_AGE", 7)
+	compress := getEnvBool("BEADS_DAEMON_LOG_COMPRESS", true)
+
+	logF := &lumberjack.Logger{
+		Filename:   d.cfg.LogFile,
+		MaxSize:    maxSizeMB,
+		MaxBackups: maxBackups,
+		MaxAge:     maxAgeDays,
+		Compress:   compress,
+	}
+
+	log := &logger{
+		logFunc: func(format string, args ...interface{}) {
+			msg := fmt.Sprintf(format, args...)
+			timestamp := time.Now().Format("2006-01-02 15:04:05")
+			_, _ = fmt.Fprintf(logF, "[%s] %s\n", timestamp, msg)
+		},
+	}
+
+	return logF, log
+}
+
+func getEnvInt(key string, defaultValue int) int {
+	if val := os.Getenv(key); val != "" {
+		if parsed, err := strconv.Atoi(val); err == nil {
+			return parsed
+		}
+	}
+	return defaultValue
+}
+
+func getEnvBool(key string, defaultValue bool) bool {
+	if val := os.Getenv(key); val != "" {
+		return val == "true" || val == "1"
+	}
+	return defaultValue
+}