Initial import: fast_dual_ws (renamed to fhd_fast_tri_ws)

FAST-LIVO2 dual/triple-camera VIO-LIO mapping workspace (ROS2 Humble),
including the N-camera port from Omni-LIVO, rpg_vikit multi-camera
parameter loader, and the um982_driver/gnss_comm packages staged here
ahead of RTK fusion work.

FAST-LIVO2 and rpg_vikit were previously separate git clones tracking
their own GitHub history (Robotic-Developer-Road org, humble/main
branches) — that history is preserved locally in
src/{FAST-LIVO2,rpg_vikit}/.git-github-backup (not pushed here) and
these two are now tracked flat as part of this repo going forward.

.gitignore

@@ -0,0 +1,17 @@
+# colcon build artifacts — regenerate with `colcon build`
+build/
+install/
+log/
+
+# local-only backup of FAST-LIVO2/rpg_vikit's original GitHub .git history —
+# kept on disk for reference, not pushed here (108MB+, and not useful as
+# plain files inside another repo's git objects)
+.git-github-backup/
+
+# Python
+__pycache__/
+*.pyc
+
+# editors
+.vscode/
+*.swp