fix(idgen): retry snowflake generation and error on negative ID

NextUint64ID now retries up to 3 times when Int64() is negative, then
returns an error instead of 0 or Fatalf. All call sites propagate the
error to avoid GORM omitting zero-value primary keys.

internal/db/idgen/snowflake.go

@@ -6,6 +6,8 @@
 package idgen
 
 import (
+	"errors"
+	"fmt"
 	"log"
 
 	"github.com/Rain-kl/Wavelet/internal/config"
@@ -15,6 +17,11 @@ import (
 // 2025-12-01 00:00:00 UTC 的毫秒时间戳
 const epoch int64 = 1764547200000
 
+const maxNegativeIDRetries = 3
+
+// ErrNegativeSnowflakeID 表示 Snowflake 在重试后仍生成负值 ID。
+var ErrNegativeSnowflakeID = errors.New("snowflake generated negative ID")
+
 var node *snowflake.Node
 
 func init() {
@@ -29,11 +36,15 @@ func init() {
 	log.Printf("[Snowflake] initialized with node ID: %d, epoch: 2025-12-01\n", nodeID)
 }
 
-// NextUint64ID 生成下一个分布式唯一 ID
-func NextUint64ID() uint64 {
-	val := node.Generate().Int64()
-	if val < 0 {
-		return 0
+// NextUint64ID 生成下一个分布式唯一 ID。
+// 理论上不应出现负值；若出现则最多重试 maxNegativeIDRetries 次，仍失败则返回错误。
+func NextUint64ID() (uint64, error) {
+	for attempt := 1; attempt <= maxNegativeIDRetries; attempt++ {
+		id := node.Generate().Int64()
+		if id >= 0 {
+			return uint64(id), nil
+		}
+		log.Printf("[Snowflake] generated negative ID: %d (attempt %d/%d)", id, attempt, maxNegativeIDRetries)
 	}
-	return uint64(val)
-}
+	return 0, fmt.Errorf("%w: failed after %d attempts", ErrNegativeSnowflakeID, maxNegativeIDRetries)
+}

internal/db/idgen/snowflake_test.go

@@ -0,0 +1,17 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package idgen
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNextUint64ID(t *testing.T) {
+	id, err := NextUint64ID()
+	require.NoError(t, err)
+	assert.NotZero(t, id)
+}