feat(frontend/vditor): 实现基于 FFmpeg.wasm 的视频压缩功能

- 添加视频压缩相关配置和工具函数
- 实现 FFmpeg.wasm 初始化和视频压缩功能
- 优化文件上传流程，支持视频文件压缩

frontend_nuxt/plugins/ffmpeg.client.ts

@@ -0,0 +1,37 @@
+import { FFmpeg } from '@ffmpeg/ffmpeg'
+import { toBlobURL } from '@ffmpeg/util'
+import { defineNuxtPlugin, useRuntimeConfig } from 'nuxt/app'
+
+let ffmpeg: FFmpeg | null = null
+
+export default defineNuxtPlugin(() => {
+  const {
+    public: { ffmpegVersion },
+  } = useRuntimeConfig()
+
+  return {
+    provide: {
+      ffmpeg: async () => {
+        if (ffmpeg) return ffmpeg
+
+        ffmpeg = new FFmpeg()
+
+        const mtOk =
+          typeof crossOriginIsolated !== 'undefined' &&
+          crossOriginIsolated &&
+          typeof SharedArrayBuffer !== 'undefined'
+
+        const pkg = mtOk ? '@ffmpeg/core-mt' : '@ffmpeg/core-st'
+        const base = `https://unpkg.com/${pkg}@${ffmpegVersion}/dist/umd`
+
+        await ffmpeg.load({
+          coreURL: await toBlobURL(`${base}/ffmpeg-core.js`, 'text/javascript'),
+          wasmURL: await toBlobURL(`${base}/ffmpeg-core.wasm`, 'application/wasm'),
+          workerURL: await toBlobURL(`${base}/ffmpeg-core.worker.js`, 'text/javascript'),
+        })
+
+        return ffmpeg
+      },
+    },
+  }
+})