feat: 新增 Amlogic AMLENC 硬件编码支持

- 新增动态加载及 ABI 校验的 AMLENC H.264/H.265 编码器
- 注册 Amlogic 后端并扩展编码器自检
- 并行执行 MJPEG 解码与 AMLENC 编码
- 复用 NV12 缓冲区并移除冗余帧初始化
- 优化低延迟帧分发及 RTCP 关键帧恢复
- 动态调整 AMLENC 码率尚未完成，效果不佳

Cargo.toml

@@ -56,6 +56,7 @@ desktop = [
     "dep:serialport",
     "dep:async-trait",
     "dep:libc",
+    "dep:libloading",
     "dep:ventoy-img",
     "dep:protobuf",
     "dep:sodiumoxide",
@@ -156,6 +157,7 @@ sdp-types = { version = "0.1", optional = true }
 serialport = { version = "4", optional = true }
 async-trait = { version = "0.1", optional = true }
 libc = { version = "0.2", optional = true }
+libloading = { version = "0.8", optional = true }
 
 # Ventoy bootable image support
 ventoy-img = { path = "libs/ventoy-img-rs", optional = true }