fix: show balances and fees below 0.000001 ETH as nonzero on the send screens (closes #343)

The stored ETH balance and the send-confirm screen's fee were each cut to six
decimal places, so a value below 0.000001 read as 0.0, and the fee no longer
matched the approval screen's. The ETH balance is now stored exactly, and the
send screen's Current balance and the send-confirm screen's balance, fee,
reserve and insufficient-balance messages go through truncateAmountNeverZero(),
as the approval screen does. Token balances keep their six-decimal value: it is
also what leaves dust off the balance list, and keeps the string within the 18
decimals the balance check reads.

Model: opus-5-5

src/popup/views/send.js

@@ -16,6 +16,7 @@ const { resolveTokenDecimals } = require("../../shared/approvalAmount");
 const { resolveSymbol } = require("../../shared/tokenList");
 const { isLowHolderCount } = require("../../shared/holders");
 const { isSpoofedSymbol } = require("../../shared/symbolSpoof");
+const { truncateAmountNeverZero } = require("../../shared/amountDisplay");
 const { getAddress } = require("ethers");
 
 const ZERO_ADDRESS = "0x0000000000000000000000000000000000000000";
@@ -150,7 +151,9 @@ function updateSendBalance() {
     const token = state.selectedToken || $("send-token").value;
     if (token === "ETH") {
         $("send-balance").textContent =
-            "Current balance: " + (addr.balance || "0") + " ETH";
+            "Current balance: " +
+            truncateAmountNeverZero(addr.balance || "0") +
+            " ETH";
     } else {
         const tb = (addr.tokenBalances || []).find(
             (t) => t.address.toLowerCase() === token.toLowerCase(),
@@ -167,7 +170,10 @@ function updateSendBalance() {
         $("send-balance").textContent =
             bal == null
                 ? "Current balance: unknown (" + symbol + ")"
-                : "Current balance: " + bal + " " + symbol;
+                : "Current balance: " +
+                  truncateAmountNeverZero(bal) +
+                  " " +
+                  symbol;
     }
 }