APDU list: the selected row gets a blue tint in dark mode too

- the selection used --bg-input (#334155, a neutral slate) in dark mode, which
  sat right next to the GET RESPONSE pair rows' grey tint
  (--pair-row = rgba(148,163,184,0.12)) and was easy to mistake for them; the
  light theme already had its own blue (#dbeafe) through a
  [data-theme="light"] override
- both themes now set a --selected-bg variable (dark #1e3a8a = blue-900 — the
  palette counterpart of the light blue-100 — light #dbeafe unchanged) and a
  single `.apdu-entry.selected` rule uses it, so the override is gone
- Node test pins the variable in both themes and the single rule
- SW cache simtrace-analyser-v90 (cosmetic, no version bump)

frontend/tests/style.test.js

@@ -27,6 +27,16 @@ test('the P3 row labels Lc and Le', () => {
 	assert.match(src, /t\('Lc \(command data length\)'\)/);
 });
 
+test('the APDU selection is a blue tint in both themes', () => {
+	assert.match(src, /\.apdu-entry\.selected \{ background: var\(--selected-bg\); \}/);
+	assert.doesNotMatch(src, /\[data-theme="light"\] \.apdu-entry\.selected/);
+	// Dark: a blue (not the neutral --bg-input grey that blended with the
+	// GET RESPONSE pair rows); light: the established blue-100.
+	assert.match(src, /--selected-bg: #1e3a8a;/);
+	assert.match(src, /--selected-bg: #dbeafe;/);
+	assert.doesNotMatch(src, /--selected-bg: var\(--bg-input\)/);
+});
+
 // ── trace topbar layout ────────────────────────────────────────────────
 
 test('the view selector sits over the side panel at the panel width', () => {