fix(web): dark-mode tokens for popup primitives + theme-color/color-scheme sync (#68)

Tooltip, toast, and combobox popups still hardcoded light colors
(bg-white, neutral-*, indigo-50) and rendered as white boxes in dark
mode; the objects-table page-size select did the same in app code.
Swap all of them to theme tokens (popover/accent/muted/destructive/
success) and replace the toast's literal "×" with the lucide X icon.

Wire browser chrome into the theme: color-scheme via CSS on
:root/.dark (follows the in-app toggle, not just the OS), a
theme-color meta kept in sync by the preload script and applyTheme(),
plus a unit test for the meta sync.

Extend check-no-raw-colors to also flag shadeless white/black
utilities outside components/ui/ so the objects-table case can't
recur.

Closes #68

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/src/index.css

@@ -35,6 +35,7 @@
 }
 
 :root {
+  color-scheme: light;
   --background: oklch(1 0 0);
   --foreground: oklch(0.145 0 0);
   --card: oklch(1 0 0);
@@ -63,6 +64,7 @@
 }
 
 .dark {
+  color-scheme: dark;
   --background: oklch(0.145 0 0);
   --foreground: oklch(0.985 0 0);
   --card: oklch(0.205 0 0);