fix: the balance lists and Home cut amounts to four decimals (closes #757)

The balance lists and Home's ETH line rounded with toFixed(4), so 0.99996
ETH read 1.0000 there and 0.9999 on Send. They now cut the stored decimal
string with truncateAmount(), as the history rows do. balanceLine() takes
the stored balance string instead of a parsed number, and escapes the
quantity cell. The screens that state what is authorized keep the floor
of truncateAmountNeverZero().

Model: opus-5-5

tests/transactions.test.js

@@ -1361,6 +1361,31 @@ describe("fetchRecentTransactions merge and dedup", () => {
         expect(txs[0].holders).toBe(3500000);
     });
 
+    // README.md, Amounts: a history row cuts to four decimals, with no floor.
+    test("a token transfer below 0.0001 reads 0.0000", async () => {
+        respondWith(
+            [],
+            [
+                {
+                    transaction_hash: "0x" + "4".repeat(64),
+                    block_number: 21000040,
+                    timestamp: TS,
+                    from: { hash: ORDINARY_PEER },
+                    to: { hash: VICTIM },
+                    total: { value: "40", decimals: "6" },
+                    token: {
+                        symbol: "USDC",
+                        address_hash: USDC_CONTRACT,
+                        holders_count: "3500000",
+                    },
+                },
+            ],
+        );
+
+        const txs = await fetchRecentTransactions(VICTIM, BLOCKSCOUT, "0x1");
+        expect(txs[0].value).toBe("0.0000");
+    });
+
     test("two transfers of the same token in one transaction collapse to one entry", async () => {
         const hash = "0x" + "3".repeat(64);
         const leg = (value) => ({