refactor(storage): drop per-upload storage_driver, use storage_config as single source

Remove w_uploads.storage_driver and route all read/write/delete paths through
storage.Active() backed by storage_config.driver. Block direct driver switches
when uploads exist; require migration task instead. Simplify migration to
cursor-based file_path iteration without per-row driver updates.

internal/apps/admin/system_config/errs.go

@@ -11,4 +11,5 @@ const (
 	ConfigKeyRequired    = "配置键不能为空"
 	ConfigValueRequired  = "配置值不能为空"
 	ConfigKeyExists      = "配置键已存在"
+	StorageDriverSwitchRequiresMigration = "存在存量文件，请通过存储迁移任务切换存储引擎"
 )

internal/apps/admin/system_config/logics.go

@@ -7,7 +7,6 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
-	"fmt"
 	"time"
 
 	"github.com/Rain-kl/Wavelet/internal/db"
@@ -88,9 +87,6 @@ func updateSystemConfig(ctx context.Context, key string, req UpdateSystemConfigR
 		if err := tx.Model(&config).Updates(updates).Error; err != nil {
 			return err
 		}
-		if err := repointUploadStorageDriversOnDriverSwitch(ctx, tx, key, originalDriver, req.Value); err != nil {
-			return err
-		}
 		resolveStorageMigrationTasksOnDirectDriverUpdate(ctx, tx, key, originalDriver, req.Value)
 		return nil
 	}); err != nil {
@@ -101,38 +97,6 @@ func updateSystemConfig(ctx context.Context, key string, req UpdateSystemConfigR
 	return nil
 }
 
-func repointUploadStorageDriversOnDriverSwitch(
-	ctx context.Context,
-	tx *gorm.DB,
-	key string,
-	originalDriver storage.Driver,
-	newValue string,
-) error {
-	if key != model.ConfigKeyStorageConfig || originalDriver == "" {
-		return nil
-	}
-
-	var newCfg storage.Config
-	if err := json.Unmarshal([]byte(newValue), &newCfg); err != nil {
-		return fmt.Errorf("parse storage config for driver repoint: %w", err)
-	}
-	if newCfg.Driver == "" || newCfg.Driver == originalDriver {
-		return nil
-	}
-
-	result := tx.Model(&model.Upload{}).
-		Where("storage_driver = ? AND status != ?", string(originalDriver), model.UploadStatusDeleted).
-		Update("storage_driver", string(newCfg.Driver))
-	if result.Error != nil {
-		return result.Error
-	}
-	if result.RowsAffected > 0 {
-		logger.InfoF(ctx, "[StorageConfig] switched driver %s -> %s, repointed %d upload records",
-			originalDriver, newCfg.Driver, result.RowsAffected)
-	}
-	return nil
-}
-
 func resolveStorageMigrationTasksOnDirectDriverUpdate(
 	ctx context.Context,
 	tx *gorm.DB,

internal/apps/admin/system_config/routers.go

@@ -18,6 +18,7 @@ import (
 	"github.com/Rain-kl/Wavelet/internal/apps/cap"
 	"github.com/Rain-kl/Wavelet/internal/apps/upload"
 	"github.com/Rain-kl/Wavelet/internal/common/response"
+	"github.com/Rain-kl/Wavelet/internal/db"
 	"github.com/Rain-kl/Wavelet/internal/model"
 	"github.com/Rain-kl/Wavelet/internal/repository"
 	"github.com/Rain-kl/Wavelet/internal/storage"
@@ -266,11 +267,13 @@ func TestSMTP(c *gin.Context) {
 
 func isStorageConfigValidationError(err error) bool {
 	msg := err.Error()
-	return strings.HasPrefix(msg, "解析") ||
+	return msg == StorageDriverSwitchRequiresMigration ||
+		strings.HasPrefix(msg, "解析") ||
 		strings.HasPrefix(msg, "验证") ||
 		strings.HasPrefix(msg, "初始化测试") ||
 		strings.HasPrefix(msg, "存储连通性") ||
-		strings.HasPrefix(msg, "序列化")
+		strings.HasPrefix(msg, "序列化") ||
+		strings.HasPrefix(msg, "检查存量文件")
 }
 
 func maskSensitiveConfig(key, value string) string {
@@ -322,6 +325,15 @@ func validateAndMergeStorageConfig(ctx context.Context, value string, currentCon
 
 func validateMergedStorageConfig(ctx context.Context, currentCfg, newCfg, targetCfg storage.Config) error {
 	if newCfg.Driver != "" && newCfg.Driver != currentCfg.Driver {
+		var uploadCount int64
+		if err := db.DB(ctx).Model(&model.Upload{}).
+			Where("status != ?", model.UploadStatusDeleted).
+			Count(&uploadCount).Error; err != nil {
+			return fmt.Errorf("检查存量文件失败: %w", err)
+		}
+		if uploadCount > 0 {
+			return errors.New(StorageDriverSwitchRequiresMigration)
+		}
 		if err := validateDriverConfig(targetCfg, newCfg.Driver); err != nil {
 			return fmt.Errorf("验证目标存储配置参数失败: %w", err)
 		}

internal/apps/admin/system_config/routers_test.go

@@ -13,6 +13,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/textproto"
+	"strings"
 	"testing"
 
 	"github.com/Rain-kl/Wavelet/internal/apps/oauth"
@@ -441,7 +442,53 @@ func TestUpdateStorageConfigValidation(t *testing.T) {
 		}
 	})
 
+	t.Run("reject driver switch when uploads exist", func(t *testing.T) {
+		upload := model.Upload{
+			ID:        88001,
+			UserID:    1,
+			FileName:  "keep.txt",
+			FilePath:  "uploads/keep.txt",
+			FileSize:  4,
+			MimeType:  "text/plain",
+			Extension: "txt",
+			Type:      "attachment",
+			Status:    model.UploadStatusUsed,
+		}
+		if err := dbConn.Create(&upload).Error; err != nil {
+			t.Fatalf("seed upload failed: %v", err)
+		}
+
+		tempDir := t.TempDir()
+		cfg := storage.DefaultConfig()
+		cfg.Driver = storage.DriverS3
+		cfg.S3.Endpoint = "http://127.0.0.1:19998"
+		cfg.S3.Region = "us-east-1"
+		cfg.S3.Bucket = "wavelet"
+		cfg.S3.AccessKeyID = "test"
+		cfg.S3.SecretAccessKey = "test"
+		cfg.Local.Root = tempDir
+
+		cfgBytes, _ := json.Marshal(cfg)
+		payload := UpdateSystemConfigRequest{Value: string(cfgBytes)}
+		body, _ := json.Marshal(payload)
+		req, _ := http.NewRequest("PUT", "/api/v1/admin/system-configs/storage_config", bytes.NewBuffer(body))
+		req.Header.Set("Content-Type", "application/json")
+		w := httptest.NewRecorder()
+		router.ServeHTTP(w, req)
+
+		if w.Code != http.StatusBadRequest {
+			t.Fatalf("expected 400 Bad Request, got %d. Body: %s", w.Code, w.Body.String())
+		}
+		if !strings.Contains(w.Body.String(), StorageDriverSwitchRequiresMigration) {
+			t.Fatalf("expected migration-required error, got: %s", w.Body.String())
+		}
+	})
+
 	t.Run("switch to local while active s3 is unreachable", func(t *testing.T) {
+		if err := dbConn.Where("1 = 1").Delete(&model.Upload{}).Error; err != nil {
+			t.Fatalf("clear uploads failed: %v", err)
+		}
+
 		activeCfg := storage.DefaultConfig()
 		activeCfg.Driver = storage.DriverS3
 		activeCfg.S3.Endpoint = "http://127.0.0.1:9999"