Refactor daemon.go for testability and maintainability (bd-2b34)

- Split 1567-line daemon.go into 5 focused modules
- daemon_config.go (122 lines): config/path resolution
- daemon_lifecycle.go (451 lines): start/stop/status/health/metrics
- daemon_sync.go (510 lines): export/import/sync logic
- daemon_server.go (115 lines): RPC server setup
- daemon_logger.go (43 lines): logging utilities
- Reduced main daemon.go to 389 lines (75% reduction)
- All tests pass, improved code organization

Amp-Thread-ID: https://ampcode.com/threads/T-7504c501-f962-4b82-a6d9-8e33f547757d
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/daemon_logger.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"gopkg.in/natefinch/lumberjack.v2"
+)
+
+// daemonLogger wraps a logging function for the daemon
+type daemonLogger struct {
+	logFunc func(string, ...interface{})
+}
+
+func (d *daemonLogger) log(format string, args ...interface{}) {
+	d.logFunc(format, args...)
+}
+
+// setupDaemonLogger creates a rotating log file logger for the daemon
+func setupDaemonLogger(logPath string) (*lumberjack.Logger, daemonLogger) {
+	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:   logPath,
+		MaxSize:    maxSizeMB,
+		MaxBackups: maxBackups,
+		MaxAge:     maxAgeDays,
+		Compress:   compress,
+	}
+
+	logger := daemonLogger{
+		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, logger
+}