Implement Set Name feature (0x6d01)

- Add MemoSetName service with 77-byte UTF-8 validation and broadcast.
- Add SetNamePage controller with byte counter and navigation to /account.
- Add AccountPage controller showing stored name and Set Name button.
- Add Profiles session store to share the new name across pages.
- Add React views /memo/set-name and /account, plus nav link.
- Update acceptance handlers for set-name scenarios and fix fake wallet
  sendOpReturn signature to match public minimal-slp-wallet API.
- Update existing post memo tests to match the corrected wallet API.

By coder.

test/unit/profiles.test.js

@@ -0,0 +1,49 @@
+/*
+  Unit tests for the session profile store (src/services/profiles.js).
+
+  The store indexes display names by BCH cash address so that pages can read
+  a name immediately after it is broadcast.
+*/
+
+'use strict'
+
+const test = require('node:test')
+const assert = require('node:assert/strict')
+
+const Profiles = require('../../src/services/profiles')
+
+test('returns null when no name has been set for an address', () => {
+  const profiles = new Profiles()
+  assert.equal(profiles.getName('bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'), null)
+})
+
+test('stores and retrieves a name by address', () => {
+  const profiles = new Profiles()
+  const addr = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+  profiles.setName(addr, 'trout')
+  assert.equal(profiles.getName(addr), 'trout')
+})
+
+test('updating a name overwrites the previous value', () => {
+  const profiles = new Profiles()
+  const addr = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+  profiles.setName(addr, 'trout')
+  profiles.setName(addr, 'salmon')
+  assert.equal(profiles.getName(addr), 'salmon')
+})
+
+test('different addresses keep independent names', () => {
+  const profiles = new Profiles()
+  const addr1 = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+  const addr2 = 'bitcoincash:qq0ktdlgekdszmxhmg7y6a90t9dpj6p0pg3gctn9e'
+  profiles.setName(addr1, 'trout')
+  profiles.setName(addr2, 'salmon')
+  assert.equal(profiles.getName(addr1), 'trout')
+  assert.equal(profiles.getName(addr2), 'salmon')
+})
+
+test('ignores setName for a missing address', () => {
+  const profiles = new Profiles()
+  profiles.setName(null, 'trout')
+  assert.equal(profiles.getName(null), null)
+})