fix: a tracked token reads quantity unknown at an address no refresh has read (closes #720)

A new address, a new wallet and a network switch each leave tracked tokens
with no balance entry, so their lines read 0.0000 before any refresh had read
them.

Each of these now sets `balanceNotFetched` on the tracked tokens, and a refresh
already clears it. Their lines read `quantity unknown` until then. Addresses
that the wallet scan finds get the same. A refresh that did not read every
address the page now holds leaves the field set.

Model: opus-5-5

src/popup/views/home.js

@@ -3,6 +3,7 @@ const {
     showView,
     showFlash,
     balanceLinesForAddress,
+    markTrackedTokensNotFetched,
     isoDate,
     timeAgo,
     addressDotHtml,
@@ -394,6 +395,7 @@ function render(ctx) {
                 tokenBalances: [],
             });
             wallet.nextIndex++;
+            markTrackedTokensNotFetched();
             await saveState();
             render(ctx);
             ctx.doRefreshAndRender();