Filter spam tokens from balance display

Token balances from Blockscout are now filtered before display.
A token only appears if it meets at least one criterion:
- In the known 511-token list (by contract address)
- Explicitly tracked by the user (added via + Token)
- Has >= 1,000 holders on-chain

Also rejects tokens spoofing a known symbol from a different
contract address (same check used for transaction filtering).

This prevents airdropped spam tokens like "OpenClaw" from
appearing in the wallet without the user ever tracking them.

src/background/index.js

@@ -497,7 +497,12 @@ async function backgroundRefresh() {
     if (now - (state.lastBalanceRefresh || 0) < BACKGROUND_REFRESH_INTERVAL)
         return;
     if (state.wallets.length === 0) return;
-    await refreshBalances(state.wallets, state.rpcUrl, state.blockscoutUrl);
+    await refreshBalances(
+        state.wallets,
+        state.rpcUrl,
+        state.blockscoutUrl,
+        state.trackedTokens,
+    );
     state.lastBalanceRefresh = now;
     await saveState();
 }