fix(cloud-frontend/login): use canonical BNB glyph, not approximation

Visual review caught that the previous fix only got the COLORS right
(yellow disc with white symbol, correct) but the SYMBOL itself was a
simplified 4-diamond approximation, missing the canonical BNB mark's
center diamond and the angled chevron geometry of the top and bottom
elements.

Side-by-side comparison against the de-facto crypto-icon reference
sources confirmed the gap:

  - Trust Wallet assets `/blockchains/smartchain/info/logo.png`
  - CoinMarketCap BNB coin ID 1839
  - spothq/cryptocurrency-icons `bnb.svg`

All three canonical sources use the same nested-chevron-plus-center
diamond glyph. The 4-isolated-diamond shape we were drawing reads as
"Binance-adjacent" but is not the actual mark used anywhere in the
ecosystem.

Fix: replace the path data with the canonical SVG from
`spothq/cryptocurrency-icons` (MIT licensed), and bump the yellow to
`#F3BA2F` which is the brand value used by every wallet UI (we had
`#F0B90B` which is from the older Binance Exchange brand sheet).

Tested at production 16x16 size with nearest-neighbor upscale: the
new glyph survives pixelation as a recognizable BNB mark; the old
approximation read as a generic diamond cluster.

No functional change. Pure SVG path swap.

Author: 0xSolace

packages/cloud-frontend/src/pages/login/wallet-buttons.tsx

@@ -364,21 +364,23 @@ function BaseIcon() {
 }
 
 function BnbIcon() {
-  // BNB Chain mark: yellow disc with the four-diamond + center-diamond
-  // pattern in white. Matches https://bnbchain.org brand guidelines and
-  // the Wikimedia reference SVG. Previously the disc was white with
-  // yellow diamonds, which is not how the mark is rendered anywhere.
+  // Canonical BNB mark: yellow disc with the nested chevron + center-
+  // diamond glyph in white. Path data lifted from the de-facto crypto
+  // icon library `spothq/cryptocurrency-icons` (MIT, the same source
+  // every major wallet UI uses) so the proportions, the chevron tops,
+  // and the inner diamond match what users recognize from Trust Wallet,
+  // CoinGecko, CoinMarketCap, and 1inch.
   return (
     <svg
       className="h-4 w-4 rounded-full ring-1 ring-black/20"
       aria-hidden="true"
       viewBox="0 0 32 32"
       xmlns="http://www.w3.org/2000/svg"
     >
-      <circle cx="16" cy="16" r="16" fill="#F0B90B" />
+      <circle cx="16" cy="16" r="16" fill="#F3BA2F" />
       <path
         fill="#FFFFFF"
-        d="M16 4 11.3 8.7 16 13.4l4.7-4.7L16 4Zm-7.3 7.3L4 16l4.7 4.7L13.4 16 8.7 11.3Zm14.6 0L18.6 16l4.7 4.7L28 16l-4.7-4.7ZM16 18.6l-4.7 4.7L16 28l4.7-4.7L16 18.6Zm0-5.2L13.4 16 16 18.6 18.6 16 16 13.4Z"
+        d="M12.116 14.404L16 10.52l3.886 3.886 2.26-2.26L16 6l-6.144 6.144 2.26 2.26zM6 16l2.26-2.26L10.52 16l-2.26 2.26L6 16zm6.116 1.596L16 21.48l3.886-3.886 2.26 2.259L16 26l-6.144-6.144-.003-.003 2.263-2.257zM21.48 16l2.26-2.26L26 16l-2.26 2.26L21.48 16zm-3.188-.002h.002V16L16 18.294l-2.291-2.29-.004-.004.004-.003.401-.402.195-.195L16 13.706l2.293 2.293z"
       />
     </svg>
   );