Replace old 150-token list with 511-token tokenList.js

Delete src/shared/tokens.js and migrate all consumers to
src/shared/tokenList.js which has 511 tokens (vs ~150) sourced
from CoinGecko with on-chain verified decimals.

- prices.js: getTopTokenPrices now from tokenList
- transactions.js: KNOWN_SYMBOLS now from tokenList (3.4x more
  symbols for spoof detection)
- send.js: KNOWN_SYMBOLS for token dropdown filtering
- approval.js: uses pre-built TOKEN_BY_ADDRESS map instead of
  constructing its own from TOKENS array
- addToken.js: uses getTopTokens(25) for quick-pick buttons
  (only top 25 shown, not all 511)

src/popup/views/addToken.js

@@ -1,5 +1,5 @@
 const { $, showView, showFlash } = require("./helpers");
-const { TOKENS } = require("../../shared/tokens");
+const { getTopTokens } = require("../../shared/tokenList");
 const { state, saveState } = require("../../shared/state");
 const { lookupTokenInfo } = require("../../shared/balances");
 const { isScamAddress } = require("../../shared/scamlist");
@@ -9,7 +9,7 @@ function show() {
     $("add-token-address").value = "";
     $("add-token-info").classList.add("hidden");
     const list = $("common-token-list");
-    list.innerHTML = TOKENS.slice(0, 25)
+    list.innerHTML = getTopTokens(25)
         .map(
             (t) =>
                 `<button class="common-token border border-border px-1 hover:bg-fg hover:text-bg cursor-pointer text-xs" data-address="${t.address}" data-symbol="${t.symbol}" data-decimals="${t.decimals}">${t.symbol}</button>`,