feat: Add FFmpeg native addon and TypeScript definitions

Introduced FFmpeg Node.js native addon binaries for multiple platforms (darwin-arm64, linux-arm64, linux-x64, win-x64) and added TypeScript type definitions for the addon interface, including video info extraction, duration detection, audio conversion, and PCM decoding.

src/common/ffmpeg-addon.ts

@@ -0,0 +1,71 @@
+/**
+ * FFmpeg Node.js Native Addon Type Definitions
+ * 
+ * This addon provides FFmpeg functionality for Node.js including:
+ * - Video information extraction with thumbnail generation
+ * - Audio/Video duration detection
+ * - Audio format conversion to NTSILK
+ * - Audio decoding to PCM
+ */
+
+/**
+ * Video information result object
+ */
+export interface VideoInfo {
+    /** Video width in pixels */
+    width: number;
+
+    /** Video height in pixels */
+    height: number;
+
+    /** Video duration in seconds */
+    duration: number;
+
+    /** Container format name (e.g., "mp4", "mkv", "avi") */
+    format: string;
+
+    /** Video codec name (e.g., "h264", "hevc", "vp9") */
+    videoCodec: string;
+
+    /** First frame thumbnail as BMP image buffer */
+    image: Buffer;
+}
+
+/**
+ * Audio PCM decoding result object
+ */
+export interface AudioPCMResult {
+    /** PCM audio data as 16-bit signed integer samples */
+    pcm: Buffer;
+
+    /** Sample rate in Hz (e.g., 44100, 48000, 24000) */
+    sampleRate: number;
+
+    /** Number of audio channels (1 for mono, 2 for stereo) */
+    channels: number;
+}
+
+/**
+ * FFmpeg interface providing all audio/video processing methods
+ */
+export interface FFmpeg {
+    /**
+     * Get video information including resolution, duration, format, codec and first frame thumbnail
+     */
+    getVideoInfo(filePath: string, format?: 'bmp' | 'bmp24'): Promise<VideoInfo>;
+
+    /**
+     * Get duration of audio or video file in seconds
+     */
+    getDuration(filePath: string): Promise<number>;
+
+    /**
+     * Convert audio file to NTSILK format (WeChat voice message format)
+     */
+    convertToNTSilkTct(inputPath: string, outputPath: string): Promise<void>;
+
+    /**
+     * Decode audio file to raw PCM data
+     */
+    decodeAudioToPCM(filePath: string): Promise<AudioPCMResult>;
+}