fix: the address screen shows a token just added at its fetched balance, not 0.0000 (closes #516)

A balance refresh that returns now draws the balances on AddressDetail or
AddressToken again when that screen is up, not only the wallet list. Their
transaction lists are left alone.

Every add path on AddToken and SettingsAddToken tracks a token through
trackToken(), which gives the tracked record `balanceNotFetched: true`. While
the field is set, the token's line reads `quantity unknown` instead of 0.0000,
and Send reads its balance as unknown. refreshBalances() now resolves with the
tracked tokens whose balance it read at every address. The popup's refresh
deletes the field from those tokens in the stored record and leaves the rest of
the stored list as it is. Removing the token removes the field, and each network
keeps its own records.

Model: opus-5-5

src/popup/views/helpers.js

@@ -418,6 +418,15 @@ function balanceLine(symbol, amount, price, tokenId) {
     );
 }
 
+// Tracks `token` on the active network, as every add path on AddToken and
+// SettingsAddToken does. The tracked record carries `balanceNotFetched: true`
+// until a balance refresh has read the token's balance at every address
+// (doRefreshAndRender() in src/popup/index.js). Until then, an address with no
+// balance row for the token shows `quantity unknown` for it, not 0.0000.
+function trackToken(token) {
+    state.trackedTokens.push({ ...token, balanceNotFetched: true });
+}
+
 function balanceLinesForAddress(addr, trackedTokens, showZero) {
     let html = balanceLine(
         nativeCurrency(),
@@ -453,7 +462,7 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
             if (isSpoofedSymbol(t.symbol, t.address)) continue;
             html += balanceLine(
                 t.symbol,
-                0,
+                t.balanceNotFetched ? null : 0,
                 getPrice(t.address),
                 t.address.toLowerCase(),
             );
@@ -833,6 +842,7 @@ module.exports = {
     flashCopyFeedback,
     balanceLine,
     balanceLinesForAddress,
+    trackToken,
     addressHoldsFunds,
     keyMaterialName,
     unknownableAmount,