feat: options dialog cleanup, menu/tree styling, light theme contrast

- Remove dead "Safe Mode" option, rename title case to "Uppercase menu items"
- Options tree: icons, themed hover/selection, mouse tracking (matches workspace tree)
- Tree item row padding (+4px) via MenuBarStyle CT_ItemViewItem for all trees
- Titlebar grows 2px when icon shown
- Menu popups: custom separator drawing, opaque background fill, flat hover highlight
- Menu bar/popup hover uses accent color (QPalette::Highlight) instead of grey
- Light theme: bump textMuted/textFaint contrast
- Dock grip widget for workspace and scanner docks

src/themes/defaults/tw.json

@@ -8,8 +8,8 @@
     "button": "#ccccd0",
     "text": "#1b1b22",
     "textDim": "#5c5c68",
-    "textMuted": "#84848e",
-    "textFaint": "#a8a8b0",
+    "textMuted": "#6a6a78",
+    "textFaint": "#8a8a94",
     "hover": "#d8d8de",
     "selected": "#d0d0d8",
     "selection": "#b4c8e8",