add typed Arrow payloads and a dora-image-view dataflow

dora-image-view takes std/media/v1/Image, and dora's compatibility graph
has no edge from std/core/v1/UInt8 to it, so wiring the two failed
`dora validate` whatever the node actually sent. Its flat-buffer fallback
would not have decoded these frames either: it reads width/height
metadata, and this node only published shape.

image and depth now go out as the Image struct, camera_info and
point_cloud as Float32 arrays and camera_state as a string, all built
against the Arrow C data interface in src/arrow so the node still links
no Arrow C++. Shape, dtype and encoding metadata are dropped where the
payload describes itself; intrinsics, frame_id and both timestamps are
unchanged. tests/run.sh covers the packing without a camera or the SDK,
round-tripping each array through pyarrow and rebuilding it under the
sanitizers.

Breaking: image_bgr is renamed to image and every payload changes shape.
dataflow_plot.yml is replaced by dataflow_view.yml, which wires the
viewer from a tag and repeats its contract in input_types so validate
checks both sides of the wiring.

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.21)
-project(dora_zed VERSION 0.2.0 LANGUAGES C CXX)
+project(dora_zed VERSION 0.3.0 LANGUAGES C CXX)
 
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_FLAGS "-fPIC")
@@ -24,6 +24,7 @@ link_directories(${ZED_LIBRARY_DIR})
 
 add_executable(dora_zed
     src/main.cc
+    src/arrow/array.cc
     src/zed/camera.cc
     src/zed/capture.cc
     ${node_bridge}