chore: 添加后端通信相关依赖

- 添加 eventsource-parser 依赖用于 SSE 事件解析
- 新增后端配置项（iccoder.backend.baseUrl 和 timeout）
- 更新 pnpm-lock.yaml 锁定依赖版本

pnpm-lock.yaml

@@ -11,6 +11,9 @@ importers:
       '@wavedrom/doppler':
         specifier: ^1.14.0
         version: 1.14.0
+      eventsource-parser:
+        specifier: ^3.0.6
+        version: 3.0.6
       iconv-lite:
         specifier: ^0.7.1
         version: 0.7.1
@@ -662,6 +665,10 @@ packages:
     resolution: {integrity: sha512-mQw+2fkQbALzQ7V0MY0IqdnXNOeTtP4r0lN9z7AAawCXgqea7bDii20AYrIBrFd/Hx0M2Ocz6S111CaFkUcb0Q==}
     engines: {node: '>=0.8.x'}
 
+  eventsource-parser@3.0.6:
+    resolution: {integrity: sha512-Vo1ab+QXPzZ4tCa8SwIHJFaSzy4R6SHf7BY79rFBDf0idraZWAkYrDjDj8uWaSm3S2TK+hJ7/t1CEmZ7jXw+pg==}
+    engines: {node: '>=18.0.0'}
+
   fast-deep-equal@3.1.3:
     resolution: {integrity: sha512-f3qQ9oQy9j2AhBe/H9VC91wLmKBCCU/gDOnKNAYG5hswO7BLKj09Hc5HYNz9cGI++xlpDCIgDaitVs03ATR84Q==}
 
@@ -2119,6 +2126,8 @@ snapshots:
 
   events@3.3.0: {}
 
+  eventsource-parser@3.0.6: {}
+
   fast-deep-equal@3.1.3: {}
 
   fast-json-stable-stringify@2.1.0: {}