feat(ext): apply color scheme on popup + vault startup

Import applyColorScheme in popup.ts and vault.ts, await it at boot,
and register a chrome.storage.onChanged listener so live color-picker
changes take effect without a reload.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

extension/src/popup/popup.ts

@@ -19,6 +19,7 @@ import { renderFieldHistory } from './components/field-history';
 import { teardown as teardownTrash } from './components/trash';
 import { teardown as teardownDevices } from './components/devices';
 import { teardown as teardownFieldHistory } from './components/field-history';
+import { applyColorScheme } from '../shared/color-scheme';
 
 // --- Escape HTML to prevent XSS ---
 export function escapeHtml(str: string): string {
@@ -215,6 +216,14 @@ function render(): void {
 // --- Init ---
 
 async function init(): Promise<void> {
+  await applyColorScheme();
+
+  chrome.storage.onChanged.addListener((changes, area) => {
+    if (area === 'sync' && 'password_display_scheme' in changes) {
+      void applyColorScheme();
+    }
+  });
+
   // Snapshot the active tab at popup-open — the fill path uses this
   // tabId/url pair so the SW can verify the tab hasn't navigated before
   // forwarding credentials (audit M5 + TOCTOU close via expectedHost).