feat: expand confirm-tx warnings — closes #114

- Refactor address warnings into src/shared/addressWarnings.js module
  - getLocalWarnings(address, options): sync checks against local lists
  - getFullWarnings(address, provider, options): async local + RPC checks
- Expand scam address list from 652 to 2417 addresses
  - Added EtherScamDB (MIT) as additional source
- Update confirmTx.js to use the new addressWarnings module

src/shared/addressWarnings.js

@@ -0,0 +1,98 @@
+// Address warning module.
+// Provides local and async (RPC-based) warning checks for Ethereum addresses.
+// Returns arrays of {type, message, severity} objects.
+
+const { isScamAddress } = require("./scamlist");
+const { isBurnAddress } = require("./constants");
+const { log } = require("./log");
+
+/**
+ * Check an address against local-only lists (scam, burn, self-send).
+ * Synchronous — no network calls.
+ *
+ * @param {string} address - The target address to check.
+ * @param {object} [options] - Optional context.
+ * @param {string} [options.fromAddress] - Sender address (for self-send check).
+ * @returns {Array<{type: string, message: string, severity: string}>}
+ */
+function getLocalWarnings(address, options = {}) {
+    const warnings = [];
+    const addr = address.toLowerCase();
+
+    if (isScamAddress(addr)) {
+        warnings.push({
+            type: "scam",
+            message:
+                "This address is on a known scam/fraud list. Do not send funds to this address.",
+            severity: "critical",
+        });
+    }
+
+    if (isBurnAddress(addr)) {
+        warnings.push({
+            type: "burn",
+            message:
+                "This is a known null/burn address. Funds sent here are permanently destroyed and cannot be recovered.",
+            severity: "critical",
+        });
+    }
+
+    if (options.fromAddress && addr === options.fromAddress.toLowerCase()) {
+        warnings.push({
+            type: "self-send",
+            message: "You are sending to your own address.",
+            severity: "warning",
+        });
+    }
+
+    return warnings;
+}
+
+/**
+ * Check an address against local lists AND via RPC queries.
+ * Async — performs network calls to check contract status and tx history.
+ *
+ * @param {string} address - The target address to check.
+ * @param {object} provider - An ethers.js provider instance.
+ * @param {object} [options] - Optional context.
+ * @param {string} [options.fromAddress] - Sender address (for self-send check).
+ * @returns {Promise<Array<{type: string, message: string, severity: string}>>}
+ */
+async function getFullWarnings(address, provider, options = {}) {
+    const warnings = getLocalWarnings(address, options);
+
+    try {
+        const code = await provider.getCode(address);
+        if (code && code !== "0x") {
+            warnings.push({
+                type: "contract",
+                message:
+                    "This address is a smart contract, not a regular wallet.",
+                severity: "warning",
+            });
+            // If it's a contract, skip the tx count check — contracts
+            // may legitimately have zero inbound EOA transactions.
+            return warnings;
+        }
+    } catch (e) {
+        log.errorf("contract check failed:", e.message);
+    }
+
+    try {
+        const txCount = await provider.getTransactionCount(address);
+        if (txCount === 0) {
+            warnings.push({
+                type: "new-address",
+                message:
+                    "This address has never sent a transaction. Double-check it is correct.",
+                severity: "info",
+            });
+        }
+    } catch (e) {
+        log.errorf("tx count check failed:", e.message);
+    }
+
+    return warnings;
+}
+
+module.exports = { getLocalWarnings, getFullWarnings };