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/approval.js

@@ -2,7 +2,7 @@ const { $, addressDotHtml, escapeHtml, showView } = require("./helpers");
 const { state, saveState } = require("../../shared/state");
 const { formatEther, formatUnits, Interface } = require("ethers");
 const { ERC20_ABI } = require("../../shared/constants");
-const { TOKENS } = require("../../shared/tokens");
+const { TOKEN_BY_ADDRESS } = require("../../shared/tokenList");
 
 const runtime =
     typeof browser !== "undefined" ? browser.runtime : chrome.runtime;
@@ -16,12 +16,6 @@ const EXT_ICON =
 
 const erc20Iface = new Interface(ERC20_ABI);
 
-// Build address→token lookup from known token list
-const TOKEN_BY_ADDRESS = new Map();
-for (const t of TOKENS) {
-    TOKEN_BY_ADDRESS.set(t.address.toLowerCase(), t);
-}
-
 function approvalAddressHtml(address) {
     const dot = addressDotHtml(address);
     const link = `https://etherscan.io/address/${address}`;