feat(i18n): 后端添加国际化支持、优化前端界面

- 后端添加并实现国际化支持
- 前端引入 vue-i18n 模块（尚未添加国际化逻辑）
- 优化用户界面样式，统一输入框和标签样式

src/main/i18n/lang/en.ts

@@ -0,0 +1,8 @@
+export default {
+  "gummy.env.missing": "DASHSCOPE_API_KEY environment variable not detected. To use the gummy engine, you need to obtain an API Key from Alibaba Cloud's Bailian platform and add it to your local environment variables.",
+  "platform.unsupported": "Unsupported platform: ",
+  "engine.start.error": "Caption engine failed to start: ",
+  "engine.output.parse.error": "Unable to parse caption engine output as a JSON object: ",
+  "engine.error": "Caption engine error: ",
+  "engine.shutdown.error": "Failed to shut down the caption engine process: "
+}