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]/macro/MacroVibesPageClient.tsx

@@ -274,12 +274,12 @@ function FundingPanel({
       }}>
         <StatBox
           label="Latest cycle"
-          value={`${snap.latest_rate_pct?.toFixed(4)}%`}
+          value={snap.latest_rate_pct == null ? '—' : `${snap.latest_rate_pct.toFixed(4)}%`}
           hint="The most recent funding payment, in % per cycle. Positive = longs pay shorts."
         />
         <StatBox
           label="Last 24h avg"
-          value={`${snap.last_24h_avg_pct?.toFixed(4)}%`}
+          value={snap.last_24h_avg_pct == null ? '—' : `${snap.last_24h_avg_pct.toFixed(4)}%`}
           hint="Average of the last 24 hours of funding cycles. Smooths out one-off prints."
         />
         <StatBox