harden: resolve or refuse the swap token scale instead of guessing 18 (closes #340)

tokenInfo() returned decimals 18 for any token absent from the bundled list, so the swap approval line rendered a real 1000.00 of a 6-decimal token as 0.000000000001. The scale is now resolved from what the wallet already holds (bundled list, tracked tokens, explorer-reported decimals) or refused outright, matching the rule set for the ERC-20 path in #306. A refusal reuses unknownDecimalsAmount(), so it reads as "base units (decimals unknown)" with no decimal point and no symbol, and the same string propagates to rawValue so no downstream screen can render a figure the approval screen refused. No new network call on the approval path. Verified green on all three CI contexts: check, e2e-chrome, e2e-firefox.

src/popup/views/approval.js

@@ -73,6 +73,14 @@ function tokenLabel(address) {
 function decodeCalldata(data, toAddress) {
     if (!data || data === "0x" || data.length < 10) return null;
 
+    // Where a token's scale is looked for, for every decoder below: the ERC-20
+    // amount line and the swap's Amount and Min. received lines resolve it the
+    // same way, and refuse to format the same way when it is nowhere.
+    const decimalsSources = {
+        trackedTokens: state.trackedTokens,
+        wallets: state.wallets,
+    };
+
     // Try ERC-20 (approve / transfer)
     try {
         const parsed = erc20Iface.parseTransaction({ data });
@@ -84,10 +92,10 @@ function decodeCalldata(data, toAddress) {
             // the wrong number, and for a token with fewer decimals than the
             // guess it is the wrong number in the direction that reads as
             // zero. See tokenAmountText().
-            const tokenDecimals = resolveTokenDecimals(toAddress, {
-                trackedTokens: state.trackedTokens,
-                wallets: state.wallets,
-            });
+            const tokenDecimals = resolveTokenDecimals(
+                toAddress,
+                decimalsSources,
+            );
             const contractLabel = tokenSymbol
                 ? tokenSymbol + " (" + toAddress + ")"
                 : toAddress;
@@ -167,7 +175,7 @@ function decodeCalldata(data, toAddress) {
     }
 
     // Try Uniswap Universal Router
-    const routerResult = uniswap.decode(data, toAddress);
+    const routerResult = uniswap.decode(data, toAddress, decimalsSources);
     if (routerResult) return routerResult;
 
     return null;