fix fresh-install build: add preflight script, restore third_party binaries, remove WebEngine dep

- Add build_preflight.sh to create obj/ dirs that git can't track (body/board/obj, panda/board/obj)
- Wire preflight into build_only.sh and launch_chffrplus.sh
- Restore missing third_party binaries (libyuv, snpe, acados, maplibre) that were text pointers
- Remove dead Qt5WebEngineWidgets dependency from UI SConscript

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

third_party/maplibre-native-qt/aarch64

@@ -1 +0,0 @@
-larch64/

third_party/maplibre-native-qt/aarch64/include/QMapLibre/Export

@@ -0,0 +1 @@
+#include "export_core.hpp"

third_party/maplibre-native-qt/aarch64/include/QMapLibre/LayerParameter

@@ -0,0 +1 @@
+#include "layer_parameter.hpp"

third_party/maplibre-native-qt/aarch64/include/QMapLibre/Map

@@ -0,0 +1 @@
+#include "map.hpp"

third_party/maplibre-native-qt/aarch64/include/QMapLibre/QMapLibre

@@ -0,0 +1 @@
+#include "qmaplibre"

third_party/maplibre-native-qt/aarch64/include/QMapLibre/Settings

@@ -0,0 +1 @@
+#include "settings.hpp"

third_party/maplibre-native-qt/aarch64/include/QMapLibre/SourceParameter

@@ -0,0 +1 @@
+#include "source_parameter.hpp"

third_party/maplibre-native-qt/aarch64/include/QMapLibre/StyleParameter

@@ -0,0 +1 @@
+#include "style_parameter.hpp"

third_party/maplibre-native-qt/aarch64/include/QMapLibre/Types

@@ -0,0 +1 @@
+#include "types.hpp"

third_party/maplibre-native-qt/aarch64/include/QMapLibre/Utils

@@ -0,0 +1 @@
+#include "utils.hpp"