Feature: Implement H.264 and AV1 hardware encoding for remote control

Remark: Need to update FFmpeg static libraries to take effort

client/CFFmpegAV1Encoder.h

@@ -0,0 +1,62 @@
+#pragma once
+
+#include "VideoEncoderBase.h"
+#include "common/config.h"
+#include <string>
+#include <vector>
+
+// 合规守护：DISABLE_FFMPEG_FOR_TEST=1 时整类移出编译单元，避免 GPL 传染（与 c0a632a 对齐）
+#if defined(_WIN64) && !DISABLE_FFMPEG_FOR_TEST
+
+struct AVCodecContext;
+struct AVFrame;
+struct AVPacket;
+
+// FFmpeg 硬编 AV1 实现。
+// 后端探测顺序：av1_nvenc (NVIDIA RTX 40+) → av1_amf (AMD RX 7000+) → av1_qsv
+// (Intel Arc / 11 代+ 部分核显)。AV1 硬编硬件门槛比 H.264 高得多 —— 没合适
+// 硬件时 open 全部失败，由 EncoderFactory 自动回退到 H.264 路径。
+//
+// 注意：FFmpeg 7.1 没有 av1_mf 兜底，因此本类的探测列表比 H.264 短一项。
+class CFFmpegAV1Encoder : public VideoEncoderBase
+{
+public:
+    CFFmpegAV1Encoder();
+    ~CFFmpegAV1Encoder() override;
+
+    bool open(const EncoderParams& params) override;
+    void close() override;
+
+    int encode(
+        uint8_t* rgb,
+        uint8_t  bpp,
+        uint32_t stride,
+        uint32_t width,
+        uint32_t height,
+        uint8_t** lppData,
+        uint32_t* lpSize,
+        int direction = 1
+    ) override;
+
+    void forceIDR() override { m_forceIDR = true; }
+    void setBitrate(int kbps) override;
+    VideoCodec codec() const override { return VideoCodec::AV1; }
+    const char* backendName() const override { return m_backend.c_str(); }
+
+private:
+    bool tryOpenBackend(const char* name, const EncoderParams& p);
+    void cleanupCodec();
+    int convertRGB24ToNV12(uint8_t* rgb, uint32_t stride,
+                           uint32_t width, uint32_t height, int direction);
+
+    AVCodecContext* m_ctx     = nullptr;
+    AVFrame*        m_frame   = nullptr;
+    AVPacket*       m_packet  = nullptr;
+    std::vector<uint8_t> m_outputBuffer;
+    std::vector<uint8_t> m_i420Scratch;
+    int64_t     m_pts       = 0;
+    bool        m_forceIDR  = false;
+    std::string m_backend;
+};
+
+#endif // _WIN64 && !DISABLE_FFMPEG_FOR_TEST