更新项目架构与存储适配器，添加用户认证功能

本次提交包含以下主要更改：
1. 更新 `.gitignore` 文件，添加对 `node_modules` 和环境变量文件的忽略。
2. 修改 `.gitmodules` 文件，替换为新的子模块 `cloudflare-worker`。
3. 新增 `ARCHITECTURE.md` 和 `PROJECT_REFACTOR_PLAN.md` 文档，详细描述项目架构和改造计划。
4. 实现用户认证功能，添加 GitHub OAuth 处理逻辑，支持 JWT 生成与解析。
5. 引入新的存储接口 `CanvasStore`，并实现相应的存储逻辑，支持用户画布的增删改查。
6. 更新 `main.go` 文件，整合新的认证与存储逻辑，优化路由设置。

这些更改旨在提升项目的可扩展性与用户体验，支持多用户环境下的画布管理与存储。

stores/aws/store.go

@@ -0,0 +1,160 @@
+package aws
+
+import (
+	"bytes"
+	"context"
+	"excalidraw-complete/core"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"path"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/config"
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+	"github.com/oklog/ulid/v2"
+)
+
+type s3Store struct {
+	s3Client *s3.Client
+	bucket   string
+}
+
+// NewStore creates a new S3-based store.
+func NewStore(bucketName string) *s3Store {
+	cfg, err := config.LoadDefaultConfig(context.TODO())
+	if err != nil {
+		log.Fatalf("unable to load SDK config, %v", err)
+	}
+
+	s3Client := s3.NewFromConfig(cfg)
+
+	return &s3Store{
+		s3Client: s3Client,
+		bucket:   bucketName,
+	}
+}
+
+// DocumentStore implementation for anonymous sharing
+func (s *s3Store) FindID(ctx context.Context, id string) (*core.Document, error) {
+	resp, err := s.s3Client.GetObject(ctx, &s3.GetObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(id),
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to get document with id %s: %v", id, err)
+	}
+	defer resp.Body.Close()
+
+	data, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read document data: %v", err)
+	}
+
+	document := core.Document{
+		Data: *bytes.NewBuffer(data),
+	}
+
+	return &document, nil
+}
+
+func (s *s3Store) Create(ctx context.Context, document *core.Document) (string, error) {
+	id := ulid.Make().String()
+
+	_, err := s.s3Client.PutObject(ctx, &s3.PutObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(id),
+		Body:   bytes.NewReader(document.Data.Bytes()),
+	})
+	if err != nil {
+		return "", fmt.Errorf("failed to upload document: %v", err)
+	}
+
+	return id, nil
+}
+
+// CanvasStore implementation for user-owned canvases
+func (s *s3Store) getCanvasKey(userID, canvasID string) string {
+	return path.Join(userID, canvasID)
+}
+
+func (s *s3Store) List(ctx context.Context, userID string) ([]*core.Canvas, error) {
+	prefix := userID + "/"
+	output, err := s.s3Client.ListObjectsV2(ctx, &s3.ListObjectsV2Input{
+		Bucket: aws.String(s.bucket),
+		Prefix: aws.String(prefix),
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to list canvases for user %s: %v", userID, err)
+	}
+
+	canvases := make([]*core.Canvas, 0, len(output.Contents))
+	for _, object := range output.Contents {
+		canvasID := path.Base(*object.Key)
+		canvas := &core.Canvas{
+			ID:        canvasID,
+			UserID:    userID,
+			Name:      canvasID, // S3 doesn't have a native 'name' field, using ID.
+			UpdatedAt: *object.LastModified,
+		}
+		canvases = append(canvases, canvas)
+	}
+
+	return canvases, nil
+}
+
+func (s *s3Store) Get(ctx context.Context, userID, id string) (*core.Canvas, error) {
+	key := s.getCanvasKey(userID, id)
+	resp, err := s.s3Client.GetObject(ctx, &s3.GetObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(key),
+	})
+	if err != nil {
+		// A specific check for NoSuchKey can be useful here.
+		if bytes.Contains([]byte(err.Error()), []byte("NoSuchKey")) {
+			return nil, fmt.Errorf("canvas not found")
+		}
+		return nil, fmt.Errorf("failed to get canvas %s: %v", id, err)
+	}
+	defer resp.Body.Close()
+
+	data, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read canvas data: %v", err)
+	}
+
+	canvas := &core.Canvas{
+		ID:        id,
+		UserID:    userID,
+		Name:      id,
+		Data:      data,
+		UpdatedAt: *resp.LastModified,
+	}
+
+	return canvas, nil
+}
+
+func (s *s3Store) Save(ctx context.Context, canvas *core.Canvas) error {
+	key := s.getCanvasKey(canvas.UserID, canvas.ID)
+	_, err := s.s3Client.PutObject(ctx, &s3.PutObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(key),
+		Body:   bytes.NewReader(canvas.Data),
+	})
+	if err != nil {
+		return fmt.Errorf("failed to save canvas %s: %v", canvas.ID, err)
+	}
+	return nil
+}
+
+func (s *s3Store) Delete(ctx context.Context, userID, id string) error {
+	key := s.getCanvasKey(userID, id)
+	_, err := s.s3Client.DeleteObject(ctx, &s3.DeleteObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(key),
+	})
+	if err != nil {
+		return fmt.Errorf("failed to delete canvas %s: %v", id, err)
+	}
+	return nil
+}