Initial commit: scan_web integrated recording UI

FastAPI backend + vanilla JS frontend for LiDAR/camera startup, camera
settings, and rosbag recording, unifying the previous scan_gui/scan_gui_dual/
scan_gui_triple desktop tools into one web app.

.hallmark/log.json

@@ -0,0 +1,12 @@
+[
+  {
+    "date": "2026-08-04",
+    "scope": "app",
+    "macrostructure": "n/a (app/dashboard — no marketing macrostructure)",
+    "theme": "custom",
+    "theme_axes": "light / grotesk-sans / cool-cobalt",
+    "vibe": "Tally-referenced modern-minimal, instrument-panel discipline",
+    "enrichment": "none",
+    "brief": "scan_web control panel redesign — hallmark applied to app UI, not a marketing page"
+  }
+]