perf(video): 新增 RKMPP DMA 采集编码通路并完善恢复逻辑

支持原生 HDMI 和 UVC 缓冲区导出，增加同步 RKMPP 编码及可选 MJPEG 硬件转码。
校验帧布局和缓冲区租约，在 DMA 不可用或编码失败时回退到复制通路。
保留自定义码率和 GOP 策略，重开采集时同步 HDMI 源帧率，并区分 UVC 超时状态。

验证：88 个视频测试通过（含 4 个新增回归测试）；ARM64 cargo check --tests 通过。

libs/hwcodec/cpp/ffmpeg_hw/rkmpp_dmabuf_ffi.h

@@ -0,0 +1,31 @@
+#pragma once
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct RkmppDmaEncoder RkmppDmaEncoder;
+// format: 0=NV12, 1=BGR24, 2=YUYV, 3=RGB24 (byte stride), 4=MJPEG (stride ignored).
+// codec: 0=H264, 1=HEVC. MJPEG is decoded to hardware NV12, then encoded.
+RkmppDmaEncoder *rkmpp_dma_new(int width, int height, int stride, int format,
+                              int codec, int fps, int kbps, int gop,
+                              const int *fds, const size_t *sizes, size_t count);
+// Synchronous input-completion boundary. On failure the encoder is destroyed
+// internally BEFORE returning, so it cannot keep reading the capture buffer.
+// Output is borrowed until the next call or destruction; copy before reusing it.
+// bytes_used must be the actual captured payload. MJPEG needs 64 bytes of
+// readable allocation headroom; never pass sizeimage as the compressed length.
+// fresh_fd=-1 reuses the original import (native HDMI). UVC supplies a new
+// export of this dequeued slot. Keep it open until replacement/free; the old
+// export can be closed AFTER this call, including on failure.
+int rkmpp_dma_encode(RkmppDmaEncoder *encoder, size_t index, size_t bytes_used, int fresh_fd, int64_t pts_us,
+                     int force_idr, const uint8_t **data, size_t *size);
+int rkmpp_dma_reconfigure(RkmppDmaEncoder *encoder, int kbps, int gop);
+void rkmpp_dma_free(RkmppDmaEncoder *encoder);
+const char *rkmpp_dma_error(void);
+
+#ifdef __cplusplus
+}
+#endif