feat: add MobileSpeedDial FAB for mobile search and actions

Always-visible FAB in bottom-right on mobile/touch devices:
- Tap to open omnibar (search actions)
- Long-press to expand secondary actions (GitHub, theme toggle)
- Non-passive `touchstart` listener for proper `preventDefault`
- `touchHandledRef` prevents click event from re-firing after touch

Hides desktop hover-zone controls on mobile since `MobileSpeedDial`
takes over. Adds bottom padding so content scrolls above the FAB.

Bumps `use-kbd` to pick up mobile-only modal history management
(swipe-back to dismiss, no history manipulation on desktop).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ryan-williams

www/package.json

@@ -37,7 +37,7 @@
     "react-plotly.js": "^2.6.0",
     "recharts": "^3.1.0",
     "uplot": "^1.6.32",
-    "use-kbd": "github:runsascoded/use-kbd#caa1afd04827fe79ff3f313cd7e01b2c08372f78",
+    "use-kbd": "github:runsascoded/use-kbd#60c4cc2dec8dee2da5616a3a1870930842dcad61",
     "use-prms": "github:runsascoded/use-prms#cf28edc59fea41899aca2ada69499cd11604f60e",
     "use-session-storage-state": "^19.0.1",
     "@rdub/agg-plot": "https://gitlab.com/runsascoded/js/agg-plot/-/archive/e9087eda0724f058d4d2657afd51d0c3f59193e6/agg-plot-e9087eda0724f058d4d2657afd51d0c3f59193e6.tar.gz"