feat(toolrate): light/dark/system theme toggle with FOUC guard

- use-theme hook: localStorage (toolrate-theme, default system), matchMedia
  change listener, shared singleton listener, sets .dark + color-scheme
- ThemeToggle: lightbulb quick toggle (light/dark) + dropdown (light/dark/system)
- Sidebar footer + mobile header + standalone login page
- inline script in index.html to apply theme pre-render (no FOUC)
- recharts axis ticks use hsl(var(--foreground)) for dark-mode readability

artifacts/toolrate/src/pages/tool-detail.tsx

@@ -697,7 +697,7 @@ export default function ToolDetail() {
                       <ResponsiveContainer width="100%" height="100%">
                         <BarChart data={usefulnessData} layout="vertical" margin={{ top: 0, right: 0, bottom: 0, left: -20 }}>
                           <XAxis type="number" hide />
-                          <YAxis dataKey="score" type="category" axisLine={false} tickLine={false} tickFormatter={(val) => `${val} ★`} />
+                          <YAxis dataKey="score" type="category" axisLine={false} tickLine={false} tickFormatter={(val) => `${val} ★`} tick={{ fill: 'hsl(var(--foreground))', fontSize: 12 }} />
                           <Tooltip cursor={{ fill: 'transparent' }} />
                           <Bar dataKey="count" fill="hsl(var(--primary))" radius={[0, 4, 4, 0]} barSize={12} />
                         </BarChart>