fix: include timezone offset in all displayed timestamps

All isoDate() functions now output proper ISO 8601 format with timezone
offset (e.g. 2026-02-28T15:30:00-08:00) instead of bare datetime strings.
Also uses 'T' separator per ISO 8601.

closes #116

src/popup/views/addressToken.js

@@ -48,18 +48,39 @@ function etherscanAddressLink(address) {
 function isoDate(timestamp) {
     const d = new Date(timestamp * 1000);
     const pad = (n) => String(n).padStart(2, "0");
+    if (state.utcTimestamps) {
+        return (
+            d.getUTCFullYear() +
+            "-" +
+            pad(d.getUTCMonth() + 1) +
+            "-" +
+            pad(d.getUTCDate()) +
+            "T" +
+            pad(d.getUTCHours()) +
+            ":" +
+            pad(d.getUTCMinutes()) +
+            ":" +
+            pad(d.getUTCSeconds()) +
+            "Z"
+        );
+    }
+    const offsetMin = -d.getTimezoneOffset();
+    const sign = offsetMin >= 0 ? "+" : "-";
+    const absOff = Math.abs(offsetMin);
+    const tzStr = sign + pad(Math.floor(absOff / 60)) + ":" + pad(absOff % 60);
     return (
         d.getFullYear() +
         "-" +
         pad(d.getMonth() + 1) +
         "-" +
         pad(d.getDate()) +
-        " " +
+        "T" +
         pad(d.getHours()) +
         ":" +
         pad(d.getMinutes()) +
         ":" +
-        pad(d.getSeconds())
+        pad(d.getSeconds()) +
+        tzStr
     );
 }