feat(ext/vault): sidebar logo before "Relicario" wordmark

Renders the 16-optimized SVG (icons/relicario-logo-16.svg) inline
before the brand text in .vault-sidebar__header. Sized to 20×20 px
with flex-shrink: 0 so it survives narrow-pane wraps. The header
already had display: flex + gap: 8px, so the layout absorbed the new
element without further changes. Popup surface is untouched (this
override is scoped to .vault-sidebar__header .brand-logo).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

CHANGELOG.md

@@ -54,6 +54,10 @@ two confirmed bugs).
 
 ### Added
 
+- **Sidebar logo in the fullscreen vault tab.** The
+  `vault-sidebar__header` now renders the 16-optimized SVG logo
+  inline before the "Relicario" wordmark (20×20 px, `flex-shrink: 0`
+  so it survives narrow-pane wraps). Popup unaffected.
 - **Password coloring (P1).** Revealed passwords in the popup
   item-detail, fullscreen item view, field-history viewer, and
   generator preview render digits and symbols in distinct colors.

extension/src/vault/vault.css

@@ -1290,6 +1290,13 @@ textarea {
   align-items: center;
   gap: 8px;
 }
+.vault-sidebar__header .brand-logo {
+  width: 20px;
+  height: 20px;
+  margin: 0;
+  display: block;
+  flex-shrink: 0;
+}
 
 .vault-sidebar__search {
   padding: 8px 12px;

extension/src/vault/vault.ts

@@ -258,6 +258,7 @@ function renderShell(app: HTMLElement): void {
     app.innerHTML = `
       <div class="vault-sidebar">
         <div class="vault-sidebar__header">
+          <img class="brand-logo" src="icons/relicario-logo-16.svg" alt="">
           <span class="brand">Relicario</span>
         </div>
         <div class="vault-sidebar__search">