feat: initial ROS2 vision pipeline with gimbal control and nginx config

- camera_node (driver_pkg): Hikrobot MvCamera SDK image capture
- vision_node (algorithm_pkg): Otsu threshold + contour detection + target tracking
- web_node (application_pkg): HTTP server with MJPEG preview and mode switch API
- gimbal_node (gimbal_control_pkg): UART serial communication per gimbal protocol
- bringup_pkg: launch file for full pipeline
- config: nginx reverse-proxy for MJPEG streaming and API routing

.gitignore

@@ -0,0 +1,28 @@
+# ROS2 colcon build artifacts
+workspace/build/
+workspace/install/
+workspace/log/
+
+# Python
+__pycache__/
+*.py[cod]
+*.egg-info/
+*.egg
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Environment
+.env
+*.log
+
+# Claude
+.claude/
+CLAUDE.md