feat(storage): add dynamic storage config and migration

Move storage backend configuration from startup YAML to system_config-backed runtime configuration. Add local, S3-compatible, R2, MinIO, OSS, and WebDAV backend support.

Add a storage migration async task using the existing task dispatch framework. Migration target config is carried in task payload, and maintenance mode is derived from task execution state.

Split upload file management and storage operations, add the admin storage configuration tab, and update migrations and Swagger docs.

internal/storage/oss.go

@@ -0,0 +1,98 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package storage
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
+	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
+)
+
+type ossBackend struct {
+	client    *oss.Client
+	bucket    string
+	keyPrefix string
+	cdnURL    string
+}
+
+func newOSSBackend(cfg ObjectConfig) (*ossBackend, error) {
+	options := oss.LoadDefaultConfig().
+		WithCredentialsProvider(credentials.NewStaticCredentialsProvider(cfg.AccessKeyID, cfg.SecretAccessKey)).
+		WithRegion(cfg.Region)
+	if cfg.Endpoint != "" {
+		options.WithEndpoint(cfg.Endpoint)
+	}
+	return &ossBackend{
+		client:    oss.NewClient(options),
+		bucket:    cfg.Bucket,
+		keyPrefix: strings.Trim(cfg.KeyPrefix, "/"),
+		cdnURL:    strings.TrimRight(cfg.CDNURL, "/"),
+	}, nil
+}
+
+func (b *ossBackend) Put(ctx context.Context, key string, body io.Reader, _ int64, _ string) (string, error) {
+	key = b.key(key)
+	_, err := b.client.PutObject(ctx, &oss.PutObjectRequest{
+		Bucket: oss.Ptr(b.bucket),
+		Key:    oss.Ptr(key),
+		Body:   body,
+	})
+	if err != nil {
+		return "", fmt.Errorf("put OSS object: %w", err)
+	}
+	return key, nil
+}
+
+func (b *ossBackend) Get(ctx context.Context, key string) (*Object, error) {
+	key = b.key(key)
+	if b.cdnURL != "" {
+		return getHTTPObject(ctx, b.cdnURL, key)
+	}
+	output, err := b.client.GetObject(ctx, &oss.GetObjectRequest{
+		Bucket: oss.Ptr(b.bucket),
+		Key:    oss.Ptr(key),
+	})
+	if err != nil {
+		return nil, fmt.Errorf("get OSS object: %w", err)
+	}
+	contentType := defaultContentType
+	if output.ContentType != nil {
+		contentType = *output.ContentType
+	}
+	return &Object{Body: output.Body, ContentLength: output.ContentLength, ContentType: contentType}, nil
+}
+
+func (b *ossBackend) Delete(ctx context.Context, key string) error {
+	_, err := b.client.DeleteObject(ctx, &oss.DeleteObjectRequest{
+		Bucket: oss.Ptr(b.bucket),
+		Key:    oss.Ptr(b.key(key)),
+	})
+	if err != nil {
+		return fmt.Errorf("delete OSS object: %w", err)
+	}
+	return nil
+}
+
+func (b *ossBackend) Test(ctx context.Context) error {
+	ok, err := b.client.IsBucketExist(ctx, b.bucket)
+	if err != nil {
+		return fmt.Errorf("access OSS bucket: %w", err)
+	}
+	if !ok {
+		return fmt.Errorf("OSS bucket %q does not exist", b.bucket)
+	}
+	return nil
+}
+
+func (b *ossBackend) key(key string) string {
+	key = strings.TrimLeft(key, "/")
+	if b.keyPrefix == "" || strings.HasPrefix(key, b.keyPrefix+"/") {
+		return key
+	}
+	return b.keyPrefix + "/" + key
+}