style(dashboard): unify Macro composite into one card + dark-mode fix

for Performance accent

User flagged the macro index box on the overview page as feeling
disjointed. Reshaped it from three stacked elements (band → track →
scale) into a single bordered card so it reads as ONE component.

  - JSX: wrap the three pieces in <div className="overview-macro-card">
  - CSS: new .overview-macro-card with tone-coloured rim (bull/bear/neutral)
  - Solid neutral-gray filled needle (was a hollow ring — looked like a
    placeholder); tone-coloured background + white inner ring + double
    shadow so it stands out on any gradient position
  - Removed the .overview-score-fill overlay — the gradient already
    encodes the spectrum; layering an opaque fill obscured it near 0
  - Thinner track (14px vs 22px), tighter scale labels, smaller pill
  - Added "TODAY · 8 INDICATORS" stamp next to the title — gives users
    a quick anchor of what they're looking at + freshness

Plus: dark-mode override for .overview-stat-card.accent (the Performance
card). It was using a cream gradient that floated as a glaring
out-of-theme block on dark mode. Mirrored the existing .kpi.accent dark
treatment so it stays visually grouped with the rest of the dashboard.

Also includes the in-flight overview rewrite from the other AI tool
(legacy /btc redirect to /macro, middleware.ts replacing proxy.ts for
Next.js routing, refactored several dashboard panels). TypeScript clean,
production build passes.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

components/nav/LanguageSwitch.tsx

@@ -19,6 +19,9 @@ function replaceLocale(pathname: string, nextLocale: Locale) {
 export default function LanguageSwitch() {
   const pathname = usePathname()
   const searchParams = useSearchParams()
+  const options: Array<{ locale: Locale; label: string }> = [
+    { locale: 'en', label: 'EN' },
+  ]
 
   const activeLocale = useMemo<Locale>(() => {
     const seg = pathname.split('/').filter(Boolean)[0]
@@ -39,10 +42,7 @@ export default function LanguageSwitch() {
         flexShrink: 0,
       }}
     >
-      {([
-        ['en', 'EN'],
-        ['zh', '中文'],
-      ] as const).map(([locale, label]) => {
+      {options.map(({ locale, label }) => {
         const active = activeLocale === locale
         const nextPath = replaceLocale(pathname || `/${defaultLocale}`, locale)
         const qs = searchParams.toString()
@@ -56,7 +56,7 @@ export default function LanguageSwitch() {
               display: 'inline-flex',
               alignItems: 'center',
               justifyContent: 'center',
-              minWidth: locale === 'zh' ? 48 : 40,
+              minWidth: 40,
               padding: '6px 10px',
               borderRadius: 999,
               border: 'none',