Initial commit: Cockpit GPU monitor plugin for NVIDIA

Native, self-contained Cockpit page (plain HTML/JS, no build step) that
polls nvidia-smi via cockpit.spawn to show live GPU utilization, memory,
temperature, power, fan speed, ~5min history sparklines, and the list of
processes using the GPU. No background systemd service; data collection
only happens while the page is open.

.gitignore

@@ -0,0 +1,3 @@
+*.swp
+.DS_Store
+Thumbs.db