Token auto-discovery, tx history, balance polling, EIP-6963, UI overhaul

Major changes:
- Fetch token balances and tx history from Blockscout API (configurable)
- Remove manual token discovery (discoverTokens) in favor of Blockscout
- HD address gap scanning on mnemonic import
- Duplicate mnemonic detection on wallet add
- EIP-6963 multi-wallet discovery + selectedAddress updates in inpage
- Two-tier balance refresh: 10s while popup open, 60s background
- Fix $0.00 flash before prices load (return null when no prices)
- No-layout-shift: min-height on total value element
- Aligned balance columns (42ch address width, consistent USD column)
- All errors use flash messages instead of off-screen error divs
- Settings gear in global title bar, add-wallet moved to settings pane
- Settings wells with light grey background, configurable Blockscout URL
- Consistent "< Back" buttons top-left on all views
- Address titles (Address 1.1, 1.2, etc.) on main and detail views
- Send view shows current balance of selected asset
- Clickable affordance policy added to README
- Shortened mnemonic backup warning
- Fix broken background script constant imports

src/shared/transactions.js

@@ -0,0 +1,108 @@
+// Transaction history fetching via Blockscout v2 API.
+// Fetches normal transactions and ERC-20 token transfers,
+// merges them, and returns the most recent entries.
+
+const { formatEther, formatUnits } = require("ethers");
+const { log } = require("./log");
+
+function formatTxValue(val) {
+    const parts = val.split(".");
+    if (parts.length === 1) return val;
+    const dec = parts[1].slice(0, 6).replace(/0+$/, "") || "0";
+    return parts[0] + "." + dec;
+}
+
+function parseTx(tx, addrLower) {
+    const from = tx.from?.hash || "";
+    const to = tx.to?.hash || "";
+    return {
+        hash: tx.hash,
+        blockNumber: tx.block_number,
+        timestamp: Math.floor(new Date(tx.timestamp).getTime() / 1000),
+        from: from,
+        to: to,
+        value: formatTxValue(formatEther(tx.value || "0")),
+        symbol: "ETH",
+        direction: from.toLowerCase() === addrLower ? "sent" : "received",
+        isError: tx.status !== "ok",
+    };
+}
+
+function parseTokenTransfer(tt, addrLower) {
+    const from = tt.from?.hash || "";
+    const to = tt.to?.hash || "";
+    const decimals = parseInt(tt.total?.decimals || "18", 10);
+    const rawValue = tt.total?.value || "0";
+    return {
+        hash: tt.transaction_hash,
+        blockNumber: tt.block_number,
+        timestamp: Math.floor(new Date(tt.timestamp).getTime() / 1000),
+        from: from,
+        to: to,
+        value: formatTxValue(formatUnits(rawValue, decimals)),
+        symbol: tt.token?.symbol || "?",
+        direction: from.toLowerCase() === addrLower ? "sent" : "received",
+        isError: false,
+    };
+}
+
+async function fetchRecentTransactions(address, blockscoutUrl, count = 25) {
+    log.debugf("fetchRecentTransactions", address);
+    const addrLower = address.toLowerCase();
+
+    const [txResp, ttResp] = await Promise.all([
+        fetch(
+            blockscoutUrl +
+                "/addresses/" +
+                address +
+                "/transactions?limit=" +
+                count,
+        ),
+        fetch(
+            blockscoutUrl +
+                "/addresses/" +
+                address +
+                "/token-transfers?limit=" +
+                count +
+                "&type=ERC-20",
+        ),
+    ]);
+
+    if (!txResp.ok) {
+        log.errorf(
+            "blockscout transactions:",
+            txResp.status,
+            txResp.statusText,
+        );
+    }
+    if (!ttResp.ok) {
+        log.errorf(
+            "blockscout token-transfers:",
+            ttResp.status,
+            ttResp.statusText,
+        );
+    }
+
+    const txJson = txResp.ok ? await txResp.json() : {};
+    const ttJson = ttResp.ok ? await ttResp.json() : {};
+
+    const txs = [];
+
+    for (const tx of txJson.items || []) {
+        txs.push(parseTx(tx, addrLower));
+    }
+
+    // Deduplicate: skip token transfers whose tx hash is already in the list
+    const seenHashes = new Set(txs.map((t) => t.hash));
+    for (const tt of ttJson.items || []) {
+        if (seenHashes.has(tt.transaction_hash)) continue;
+        txs.push(parseTokenTransfer(tt, addrLower));
+    }
+
+    txs.sort((a, b) => b.blockNumber - a.blockNumber);
+    const result = txs.slice(0, count);
+    log.debugf("fetchRecentTransactions done, count:", result.length);
+    return result;
+}
+
+module.exports = { fetchRecentTransactions };