feat(mcp): add SSE (Server-Sent Events) transport type support

Add comprehensive support for SSE transport type to MCP server configuration,
enabling real-time streaming connections alongside existing stdio and http types.

Backend Changes:
- Add SSE type validation in mcp.rs validate_server_spec()
- Extend Codex TOML import/export to handle SSE servers
- Update claude_mcp.rs legacy API for backward compatibility
- Unify http/sse handling in json_server_to_toml_table()

Frontend Changes:
- Extend McpServerSpec type definition to include "sse"
- Add SSE radio button to configuration wizard UI
- Update wizard form logic to handle SSE url and headers
- Add SSE validation in McpFormModal submission

Validation & Error Handling:
- Add SSE support in useMcpValidation hook (TOML/JSON)
- Extend tomlUtils normalizeServerConfig for SSE parsing
- Update Zod schemas (common.ts, mcp.ts) with SSE enum
- Add SSE error message mapping in errorUtils

Internationalization:
- Add "typeSse" translations (zh: "sse", en: "sse")

Tests:
- Add SSE validation test cases in useMcpValidation.test.tsx

SSE Configuration Format:
{
  "type": "sse",
  "url": "https://api.example.com/sse",
  "headers": { "Authorization": "Bearer token" }
}

src/types.ts

@@ -112,13 +112,13 @@ export interface Settings {
 // MCP 服务器连接参数（宽松：允许扩展字段）
 export interface McpServerSpec {
   // 可选：社区常见 .mcp.json 中 stdio 配置可不写 type
-  type?: "stdio" | "http";
+  type?: "stdio" | "http" | "sse";
   // stdio 字段
   command?: string;
   args?: string[];
   env?: Record<string, string>;
   cwd?: string;
-  // http 字段
+  // http 和 sse 字段
   url?: string;
   headers?: Record<string, string>;
   // 通用字段