feat: expand warning types for send confirmation

- Combine MEW darklist (652) and CryptoScamDB (2043) into 2314 scam addresses
- Add null/burn address detection with permanent loss warning
- Add contract address detection warning (sending directly to contracts)
- Unify all warnings into single warnings element (sync + async)
- Zero-history warning now uses unified warning system

Closes #114

src/popup/views/addWallet.js

@@ -97,26 +97,18 @@ async function importMnemonic(ctx) {
     const pw = validatePassword();
     if (!pw) return;
     const { xpub, firstAddress } = hdWalletFromMnemonic(mnemonic);
-    const addrDup = state.wallets.find((w) =>
-        w.addresses.some(
-            (a) => a.address.toLowerCase() === firstAddress.toLowerCase(),
-        ),
+    const duplicate = state.wallets.find(
+        (w) =>
+            w.type === "hd" &&
+            w.addresses[0] &&
+            w.addresses[0].address.toLowerCase() === firstAddress.toLowerCase(),
     );
-    if (addrDup) {
+    if (duplicate) {
         showFlash(
-            "An address from this phrase already exists in " +
-                addrDup.name +
-                ".",
+            "This recovery phrase is already added (" + duplicate.name + ").",
         );
         return;
     }
-    const xpubDup = state.wallets.find(
-        (w) => (w.type === "hd" || w.type === "xprv") && w.xpub === xpub,
-    );
-    if (xpubDup) {
-        showFlash("This recovery phrase matches " + xpubDup.name + ".");
-        return;
-    }
     const encrypted = await encryptWithPassword(mnemonic, pw);
     const walletNum = state.wallets.length + 1;
     const wallet = {
@@ -170,11 +162,16 @@ async function importPrivateKey(ctx) {
     }
     const pw = validatePassword();
     if (!pw) return;
-    const duplicate = state.wallets.find((w) =>
-        w.addresses.some((a) => a.address.toLowerCase() === addr.toLowerCase()),
+    const duplicate = state.wallets.find(
+        (w) =>
+            w.type === "key" &&
+            w.addresses[0] &&
+            w.addresses[0].address.toLowerCase() === addr.toLowerCase(),
     );
     if (duplicate) {
-        showFlash("This address already exists in " + duplicate.name + ".");
+        showFlash(
+            "This private key is already added (" + duplicate.name + ").",
+        );
         return;
     }
     const encrypted = await encryptWithPassword(key, pw);
@@ -211,22 +208,14 @@ async function importXprvKey(ctx) {
         return;
     }
     const { xpub, firstAddress } = result;
-    const addrDup = state.wallets.find((w) =>
-        w.addresses.some(
-            (a) => a.address.toLowerCase() === firstAddress.toLowerCase(),
-        ),
+    const duplicate = state.wallets.find(
+        (w) =>
+            (w.type === "hd" || w.type === "xprv") &&
+            w.addresses[0] &&
+            w.addresses[0].address.toLowerCase() === firstAddress.toLowerCase(),
     );
-    if (addrDup) {
-        showFlash(
-            "An address from this key already exists in " + addrDup.name + ".",
-        );
-        return;
-    }
-    const xpubDup = state.wallets.find(
-        (w) => (w.type === "hd" || w.type === "xprv") && w.xpub === xpub,
-    );
-    if (xpubDup) {
-        showFlash("This key matches " + xpubDup.name + ".");
+    if (duplicate) {
+        showFlash("This key is already added (" + duplicate.name + ").");
         return;
     }
     const pw = validatePassword();

src/popup/views/confirmTx.js

@@ -24,7 +24,7 @@ const { getSignerForAddress } = require("../../shared/wallet");
 const { decryptWithPassword } = require("../../shared/vault");
 const { formatUsd, getPrice } = require("../../shared/prices");
 const { getProvider } = require("../../shared/balances");
-const { isScamAddress } = require("../../shared/scamlist");
+const { isScamAddress, isNullOrBurnAddress } = require("../../shared/scamlist");
 const { ERC20_ABI } = require("../../shared/constants");
 const { log } = require("../../shared/log");
 const makeBlockie = require("ethereum-blockies-base64");
@@ -38,6 +38,28 @@ const EXT_ICON =
     `</svg></span>`;
 
 let pendingTx = null;
+// Track active warnings so async checks can append without overwriting.
+let activeWarnings = [];
+
+function renderWarnings(el, warnings) {
+    activeWarnings = warnings.slice();
+    if (warnings.length > 0) {
+        el.innerHTML = warnings
+            .map(
+                (w) =>
+                    `<div class="border border-border border-dashed p-2 mb-1 text-xs font-bold">WARNING: ${w}</div>`,
+            )
+            .join("");
+        el.classList.remove("hidden");
+    } else {
+        el.classList.add("hidden");
+    }
+}
+
+function appendWarning(el, message) {
+    activeWarnings.push(message);
+    renderWarnings(el, activeWarnings);
+}
 
 function restore() {
     const d = state.viewData;
@@ -165,29 +187,24 @@ function show(txInfo) {
         $("confirm-balance").textContent = valueWithUsd(bal + " ETH", balUsd);
     }
 
-    // Check for warnings
+    // Check for warnings (synchronous checks first, async checks added later)
     const warnings = [];
     if (isScamAddress(txInfo.to)) {
         warnings.push(
             "This address is on a known scam/fraud list. Do not send funds to this address.",
         );
     }
+    if (isNullOrBurnAddress(txInfo.to)) {
+        warnings.push(
+            "This is a null or burn address. Funds sent here will be permanently lost.",
+        );
+    }
     if (txInfo.to.toLowerCase() === txInfo.from.toLowerCase()) {
         warnings.push("You are sending to your own address.");
     }
 
     const warningsEl = $("confirm-warnings");
-    if (warnings.length > 0) {
-        warningsEl.innerHTML = warnings
-            .map(
-                (w) =>
-                    `<div class="border border-border border-dashed p-2 mb-1 text-xs font-bold">WARNING: ${w}</div>`,
-            )
-            .join("");
-        warningsEl.classList.remove("hidden");
-    } else {
-        warningsEl.classList.add("hidden");
-    }
+    renderWarnings(warningsEl, warnings);
 
     // Check for errors
     const errors = [];
@@ -243,8 +260,11 @@ function show(txInfo) {
     state.viewData = { pendingTx: txInfo };
     showView("confirm-tx");
 
-    // Reset recipient warning to hidden (space always reserved, no layout shift)
-    $("confirm-recipient-warning").style.visibility = "hidden";
+    // Hide the legacy recipient warning element (warnings now unified)
+    const legacyWarningEl = $("confirm-recipient-warning");
+    if (legacyWarningEl) {
+        legacyWarningEl.style.display = "none";
+    }
 
     estimateGas(txInfo);
     checkRecipientHistory(txInfo);
@@ -291,19 +311,24 @@ async function estimateGas(txInfo) {
 }
 
 async function checkRecipientHistory(txInfo) {
-    const el = $("confirm-recipient-warning");
+    const warningsEl = $("confirm-warnings");
     try {
         const provider = getProvider(state.rpcUrl);
-        // Skip warning for contract addresses — they may legitimately
-        // have zero outgoing transactions (getTransactionCount returns
-        // the nonce, i.e. sent-tx count only).
         const code = await provider.getCode(txInfo.to);
         if (code && code !== "0x") {
+            // Recipient is a contract address — warn the user
+            appendWarning(
+                warningsEl,
+                "The recipient is a contract address. Sending tokens directly to a contract may result in permanent loss of funds.",
+            );
             return;
         }
         const txCount = await provider.getTransactionCount(txInfo.to);
         if (txCount === 0) {
-            el.style.visibility = "visible";
+            appendWarning(
+                warningsEl,
+                "The recipient address has ZERO transaction history. This may indicate a fresh or unused address. Double-check the address before sending.",
+            );
         }
     } catch (e) {
         log.errorf("recipient history check failed:", e.message);