chore: remove dead exports and share copied view helpers (closes #168)

AddressDetail and AddressToken defined their own isoDate() and
timeAgo(), hiding the shared pair in helpers.js, so a fix there would
not have reached them. The copies were identical and are deleted;
blockieHtml() and tokenLabel(), each defined twice, move to helpers.js.
A new test shows the history rows and the transaction detail view
write the time with the shared pair.

Deleted as never called: explorerLink(), ETHEREUM_SEPOLIA_CHAIN_ID,
getWalletValue() and getTotalValue() with their tests. Home's "Total:"
is the active address's total, as README.md already says.
addressColor() and etherscanAddressUrl() are no longer exported.

Model: opus-5-5

tests/addressValue.test.js

@@ -22,8 +22,6 @@ const {
     prices,
     clearPrices,
     getAddressValue,
-    getWalletValue,
-    getTotalValue,
     formatAddressTotal,
 } = require("../src/shared/prices");
 const { state } = require("../src/shared/state");
@@ -136,17 +134,6 @@ describe("the value of an address, and whether it is the whole value", () => {
             partial: false,
         });
     });
-
-    test("one unpriced holding makes a wallet and the grand total partial", () => {
-        const wallet = { addresses: [FULLY_PRICED, UNPRICED_ONLY] };
-        expect(getWalletValue(wallet)).toEqual({ usd: 5500, partial: true });
-        expect(getTotalValue([wallet])).toEqual({ usd: 5500, partial: true });
-    });
-
-    test("a wallet of fully priced addresses stays complete", () => {
-        const wallet = { addresses: [FULLY_PRICED, EMPTY] };
-        expect(getWalletValue(wallet)).toEqual({ usd: 5500, partial: false });
-    });
 });
 
 describe("how that value is written on screen", () => {