fix: 3 display bugs found in full-page audit

1. MacroVibesPageClient — funding stats rendered "undefined%" when
   latest_rate_pct / last_24h_avg_pct were null. `?.toFixed()` returns
   undefined inside a template literal → shows as the string "undefined%".
   Fixed: explicit null check → '—' fallback.

2. SettingsClient — broken internal anchor: href="#btc-settings-panel"
   but the section id is "btc-settings". "Open panel ↓" link did nothing.
   Fixed: corrected href to "#btc-settings".

3. KolPageClient — undefined CSS variables throughout the file:
   --bg-card (transparent) and --border (no border) were never defined
   in the design system (globals.css uses --surface and --line).
   KOL cards rendered with transparent bg and invisible borders.
   Fixed: --bg-card → --surface, --border → --line, --accent → --amber.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/[locale]/settings/SettingsClient.tsx

@@ -85,7 +85,7 @@ export default function SettingsClient() {
           <div className="settings-scope-copy">
             Strategy mode, BTC leverage, and de-risk behavior used by the Macro Vibes sleeve.
           </div>
-          <a href="#btc-settings-panel" className="settings-scope-link">Open panel ↓</a>
+          <a href="#btc-settings" className="settings-scope-link">Open panel ↓</a>
         </section>
 
         <section id="global-settings" className="settings-scope-card global">