重构认证流程，合并 GitHub 和 OIDC 登录路由，更新回调 URL，简化环境变量配置，移除旧的 Dex 相关代码，增强代码可读性和维护性。更新文档以反映新的认证流程和环境变量设置。

README.md

@@ -63,7 +63,7 @@ You must configure GitHub OAuth and a JWT secret for the application to function
 
 - `GITHUB_CLIENT_ID`: Your GitHub OAuth App's Client ID.
 - `GITHUB_CLIENT_SECRET`: Your GitHub OAuth App's Client Secret.
-- `GITHUB_REDIRECT_URL`: The callback URL. For local testing, this is `http://localhost:3002/auth/github/callback`.
+- `GITHUB_REDIRECT_URL`: The callback URL. For local testing, this is `http://localhost:3002/auth/callback`.
 - `JWT_SECRET`: A strong, random string for signing session tokens. Generate one with `openssl rand -base64 32`.
 - `OPENAI_API_KEY`: Your secret key from OpenAI.
 - `OPENAI_BASE_URL`: (Optional) For using compatible APIs like Azure OpenAI.
@@ -97,7 +97,7 @@ Create a `.env` file in the project root and add the following, filling in your
 # Get from https://github.com/settings/developers
 GITHUB_CLIENT_ID=your_github_client_id
 GITHUB_CLIENT_SECRET=your_github_client_secret
-GITHUB_REDIRECT_URL=http://localhost:3002/auth/github/callback
+GITHUB_REDIRECT_URL=http://localhost:3002/auth/callback
 
 # Generate with: openssl rand -base64 32
 JWT_SECRET=your_super_secret_jwt_string
@@ -129,7 +129,7 @@ docker build -t excalidraw-complete -f excalidraw-complete.Dockerfile .
 docker run -p 3002:3002 \
   -e GITHUB_CLIENT_ID="your_id" \
   -e GITHUB_CLIENT_SECRET="your_secret" \
-  -e GITHUB_REDIRECT_URL="http://localhost:3002/auth/github/callback" \
+  -e GITHUB_REDIRECT_URL="http://localhost:3002/auth/callback" \
   -e JWT_SECRET="your_jwt_secret" \
   -e STORAGE_TYPE="sqlite" \
   -e DATA_SOURCE_NAME="excalidraw.db" \