feat(sora): 新增 Sora 平台支持并修复高危安全和性能问题

新增功能：
- 新增 Sora 账号管理和 OAuth 认证
- 新增 Sora 视频/图片生成 API 网关
- 新增 Sora 任务调度和缓存机制
- 新增 Sora 使用统计和计费支持
- 前端增加 Sora 平台配置界面

安全修复（代码审核）：
- [SEC-001] 限制媒体下载响应体大小（图片 20MB、视频 200MB），防止 DoS 攻击
- [SEC-002] 限制 SDK API 响应大小（1MB），防止内存耗尽
- [SEC-003] 修复 SSRF 风险，添加 URL 验证并强制使用代理配置

BUG 修复（代码审核）：
- [BUG-001] 修复 for 循环内 defer 累积导致的资源泄漏
- [BUG-002] 修复图片并发槽位获取失败时已持有锁未释放的永久泄漏

性能优化（代码审核）：
- [PERF-001] 添加 Sentinel Token 缓存（3 分钟有效期），减少 PoW 计算开销

技术细节：
- 使用 io.LimitReader 限制所有外部输入的大小
- 添加 urlvalidator 验证防止 SSRF 攻击
- 使用 sync.Map 实现线程安全的包级缓存
- 优化并发槽位管理，添加 releaseAll 模式防止泄漏

影响范围：
- 后端：新增 Sora 相关数据模型、服务、网关和管理接口
- 前端：新增 Sora 平台配置、账号管理和监控界面
- 配置：新增 Sora 相关配置项和环境变量

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/internal/pkg/sora/character.go

@@ -0,0 +1,148 @@
+package sora
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"mime/multipart"
+	"net/http"
+	"net/textproto"
+)
+
+// UploadCharacterVideo uploads a character video and returns cameo ID.
+func (c *Client) UploadCharacterVideo(ctx context.Context, opts RequestOptions, data []byte) (string, error) {
+	if len(data) == 0 {
+		return "", errors.New("video data empty")
+	}
+	var buf bytes.Buffer
+	writer := multipart.NewWriter(&buf)
+	if err := writeMultipartFile(writer, "file", "video.mp4", "video/mp4", data); err != nil {
+		return "", err
+	}
+	if err := writer.WriteField("timestamps", "0,3"); err != nil {
+		return "", err
+	}
+	if err := writer.Close(); err != nil {
+		return "", err
+	}
+	resp, err := c.doRequest(ctx, "POST", "/characters/upload", opts, &buf, writer.FormDataContentType(), false)
+	if err != nil {
+		return "", err
+	}
+	return stringFromJSON(resp, "id"), nil
+}
+
+// GetCameoStatus returns cameo processing status.
+func (c *Client) GetCameoStatus(ctx context.Context, opts RequestOptions, cameoID string) (map[string]any, error) {
+	if cameoID == "" {
+		return nil, errors.New("cameo id empty")
+	}
+	return c.doRequest(ctx, "GET", "/project_y/cameos/in_progress/"+cameoID, opts, nil, "", false)
+}
+
+// DownloadCharacterImage downloads character avatar image data.
+func (c *Client) DownloadCharacterImage(ctx context.Context, opts RequestOptions, imageURL string) ([]byte, error) {
+	if c.upstream == nil {
+		return nil, errors.New("upstream is nil")
+	}
+	req, err := http.NewRequestWithContext(ctx, "GET", imageURL, nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("User-Agent", defaultDesktopUA)
+	resp, err := c.upstream.DoWithTLS(req, opts.ProxyURL, opts.AccountID, opts.AccountConcurrency, c.enableTLSFingerprint)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		return nil, fmt.Errorf("download image failed: %d", resp.StatusCode)
+	}
+	return io.ReadAll(resp.Body)
+}
+
+// UploadCharacterImage uploads character avatar and returns asset pointer.
+func (c *Client) UploadCharacterImage(ctx context.Context, opts RequestOptions, data []byte) (string, error) {
+	if len(data) == 0 {
+		return "", errors.New("image data empty")
+	}
+	var buf bytes.Buffer
+	writer := multipart.NewWriter(&buf)
+	if err := writeMultipartFile(writer, "file", "profile.webp", "image/webp", data); err != nil {
+		return "", err
+	}
+	if err := writer.WriteField("use_case", "profile"); err != nil {
+		return "", err
+	}
+	if err := writer.Close(); err != nil {
+		return "", err
+	}
+	resp, err := c.doRequest(ctx, "POST", "/project_y/file/upload", opts, &buf, writer.FormDataContentType(), false)
+	if err != nil {
+		return "", err
+	}
+	return stringFromJSON(resp, "asset_pointer"), nil
+}
+
+// FinalizeCharacter finalizes character creation and returns character ID.
+func (c *Client) FinalizeCharacter(ctx context.Context, opts RequestOptions, cameoID, username, displayName, assetPointer string) (string, error) {
+	payload := map[string]any{
+		"cameo_id":               cameoID,
+		"username":               username,
+		"display_name":           displayName,
+		"profile_asset_pointer":  assetPointer,
+		"instruction_set":        nil,
+		"safety_instruction_set": nil,
+	}
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return "", err
+	}
+	resp, err := c.doRequest(ctx, "POST", "/characters/finalize", opts, bytes.NewReader(body), "application/json", false)
+	if err != nil {
+		return "", err
+	}
+	if character, ok := resp["character"].(map[string]any); ok {
+		if id, ok := character["character_id"].(string); ok {
+			return id, nil
+		}
+	}
+	return "", nil
+}
+
+// SetCharacterPublic marks character as public.
+func (c *Client) SetCharacterPublic(ctx context.Context, opts RequestOptions, cameoID string) error {
+	payload := map[string]any{"visibility": "public"}
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return err
+	}
+	_, err = c.doRequest(ctx, "POST", "/project_y/cameos/by_id/"+cameoID+"/update_v2", opts, bytes.NewReader(body), "application/json", false)
+	return err
+}
+
+// DeleteCharacter deletes a character by ID.
+func (c *Client) DeleteCharacter(ctx context.Context, opts RequestOptions, characterID string) error {
+	if characterID == "" {
+		return nil
+	}
+	_, err := c.doRequest(ctx, "DELETE", "/project_y/characters/"+characterID, opts, nil, "", false)
+	return err
+}
+
+func writeMultipartFile(writer *multipart.Writer, field, filename, contentType string, data []byte) error {
+	header := make(textproto.MIMEHeader)
+	header.Set("Content-Disposition", fmt.Sprintf(`form-data; name="%s"; filename="%s"`, field, filename))
+	if contentType != "" {
+		header.Set("Content-Type", contentType)
+	}
+	part, err := writer.CreatePart(header)
+	if err != nil {
+		return err
+	}
+	_, err = part.Write(data)
+	return err
+}