feat(server): implement management endpoints and redis sync

Enable full resource management via API and support data plane
synchronization.

- Add CRUD handlers for Providers, Models, and Keys using DTOs
- Implement LogWriter service for asynchronous, batched audit logging
- Update SyncService to snapshot full configuration state to Redis
- Register new API routes and initialize background services
- Add configuration options for logging performance tuning

internal/service/logger.go

@@ -0,0 +1,79 @@
+package service
+
+import (
+	"context"
+	"log"
+	"time"
+
+	"github.com/ez-api/ez-api/internal/model"
+	"gorm.io/gorm"
+)
+
+// LogWriter batches log records to reduce IO overhead.
+type LogWriter struct {
+	ch            chan model.LogRecord
+	batchSize     int
+	flushInterval time.Duration
+	db            *gorm.DB
+}
+
+func NewLogWriter(db *gorm.DB, queueCapacity, batchSize int, flushInterval time.Duration) *LogWriter {
+	if batchSize <= 0 {
+		batchSize = 10
+	}
+	if queueCapacity <= 0 {
+		queueCapacity = 1000
+	}
+	if flushInterval <= 0 {
+		flushInterval = time.Second
+	}
+	return &LogWriter{
+		ch:            make(chan model.LogRecord, queueCapacity),
+		batchSize:     batchSize,
+		flushInterval: flushInterval,
+		db:            db,
+	}
+}
+
+// Start begins a background writer. Should be called once at startup.
+func (w *LogWriter) Start(ctx context.Context) {
+	go func() {
+		ticker := time.NewTicker(w.flushInterval)
+		defer ticker.Stop()
+
+		buf := make([]model.LogRecord, 0, w.batchSize)
+		flush := func() {
+			if len(buf) == 0 {
+				return
+			}
+			if err := w.db.Create(&buf).Error; err != nil {
+				log.Printf("log batch insert failed: %v", err)
+			}
+			buf = buf[:0]
+		}
+
+		for {
+			select {
+			case <-ctx.Done():
+				flush()
+				return
+			case rec := <-w.ch:
+				buf = append(buf, rec)
+				if len(buf) >= w.batchSize {
+					flush()
+				}
+			case <-ticker.C:
+				flush()
+			}
+		}
+	}()
+}
+
+// Write queues a log record; drops silently if buffer is full to protect performance.
+func (w *LogWriter) Write(rec model.LogRecord) {
+	select {
+	case w.ch <- rec:
+	default:
+		// drop to avoid blocking hot path
+	}
+}