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/components/mcp/McpFormModal.tsx

@@ -346,7 +346,10 @@ const McpFormModal: React.FC<McpFormModalProps> = ({
       toast.error(t("mcp.error.commandRequired"), { duration: 3000 });
       return;
     }
-    if (serverSpec?.type === "http" && !serverSpec?.url?.trim()) {
+    if (
+      (serverSpec?.type === "http" || serverSpec?.type === "sse") &&
+      !serverSpec?.url?.trim()
+    ) {
       toast.error(t("mcp.wizard.urlRequired"), { duration: 3000 });
       return;
     }