feat(ext/icons): replace idfoto ID-card icon with reliquary design

The prior icon was a holdover from the pre-rename idfoto project — a
stylized ID card with a portrait silhouette. Replaced with a proper
reliquary: an arched vessel with a horizontal seal band, small rivets,
standing on a blue pedestal, with a faceted gem at center representing
the protected relic.

- relicario-logo.svg: full 128-px-native design used by the setup
  wizard header and rasterized to icon-48.png and icon-128.png.
- relicario-logo-16.svg: 16-px-optimized variant (bolder strokes, no
  rivets, single-facet gem) for crisp toolbar rendering.
- Palette matches the gh-dark aesthetic used across the extension
  (#0d1117 / #161b22 background, #58a6ff / #79c0ff / #1f6feb accents).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

extension/icons/relicario-logo-16.svg

@@ -0,0 +1,24 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" fill="none">
+  <!-- 16x16-optimized: bolder strokes, simplified details, single gem
+       facet for crisp pixels at toolbar size. -->
+
+  <!-- Base plate -->
+  <rect x="1" y="13" width="14" height="2" rx="0.5" fill="#58a6ff"/>
+
+  <!-- Arched reliquary body -->
+  <path d="M 3 13
+           L 3 6
+           C 3 3.5, 5 2, 8 2
+           C 11 2, 13 3.5, 13 6
+           L 13 13 Z"
+        fill="#161b22"
+        stroke="#58a6ff"
+        stroke-width="1"
+        stroke-linejoin="round"/>
+
+  <!-- Seal band -->
+  <rect x="3" y="6" width="10" height="1" fill="#58a6ff"/>
+
+  <!-- Central gem — a simple filled diamond -->
+  <path d="M 8 8 L 10 10 L 8 12 L 6 10 Z" fill="#58a6ff"/>
+</svg>

extension/icons/relicario-logo.svg

@@ -1,30 +1,38 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 128 128" fill="none">
-  <!-- ID card outer body -->
+  <!-- relicario: a reliquary — a vessel that holds precious things.
-  <rect x="16" y="20" width="96" height="88" rx="6" fill="#0d1117" stroke="#58a6ff" stroke-width="3"/>
+       Arched container with a horizontal seal band, a central gem
+       (the "relic"), standing on a base plate.
+       Palette: gh-dark #0d1117/#161b22 background, #58a6ff primary,
+       #79c0ff / #1f6feb gem facets. -->
 
-  <!-- Photo rectangle (left side, dominant) -->
+  <!-- Base plate / pedestal — extends slightly beyond the body. -->
-  <rect x="26" y="32" width="44" height="64" rx="2" fill="#58a6ff"/>
+  <rect x="18" y="104" width="92" height="10" rx="2" fill="#58a6ff"/>
+  <rect x="18" y="112" width="92" height="2" fill="#1f6feb"/>
 
-  <!-- Silhouette in photo (cartoony connected portrait) -->
+  <!-- Reliquary body: rounded arch over a rectangular casket. -->
-  <path d="M 28 96
+  <path d="M 28 104
-           L 28 92
+           L 28 54
-           C 28 84, 34 79, 42 77
+           C 28 34, 44 20, 64 20
-           L 42 73
+           C 84 20, 100 34, 100 54
-           C 38 71, 36 66, 36 60
+           L 100 104 Z"
-           C 36 52, 41 46, 48 46
+        fill="#161b22"
-           C 55 46, 60 52, 60 60
+        stroke="#58a6ff"
-           C 60 66, 58 71, 54 73
+        stroke-width="4"
-           L 54 77
+        stroke-linejoin="round"/>
-           C 62 79, 68 84, 68 92
-           L 68 96 Z" fill="#0d1117"/>
 
-  <!-- Info lines (right side, suggest text without being text) -->
+  <!-- Horizontal seal band across the arch-to-body transition. -->
-  <rect x="78" y="36" width="24" height="4" rx="1" fill="#58a6ff"/>
+  <rect x="26" y="56" width="76" height="5" fill="#58a6ff"/>
-  <rect x="78" y="48" width="20" height="3" rx="1" fill="#30363d"/>
+
-  <rect x="78" y="56" width="24" height="3" rx="1" fill="#30363d"/>
+  <!-- Small rivets at each end of the seal band. -->
-  <rect x="78" y="64" width="18" height="3" rx="1" fill="#30363d"/>
+  <circle cx="32" cy="58.5" r="2" fill="#0d1117"/>
-  <!-- Lock icon (security indicator) -->
+  <circle cx="96" cy="58.5" r="2" fill="#0d1117"/>
-  <rect x="82" y="84" width="16" height="12" rx="1.5" fill="#3fb950"/>
+
-  <path d="M85 84 V79 A5 5 0 0 1 95 79 V84" fill="none" stroke="#3fb950" stroke-width="2.5" stroke-linecap="round"/>
+  <!-- The relic: a faceted diamond/gem centered in the casket chamber.
-  <circle cx="90" cy="90" r="1.5" fill="#0d1117"/>
+       Three tones suggest light hitting facets. -->
+  <g transform="translate(64, 80)">
+    <path d="M 0 -18 L 16 0 L 0 22 L -16 0 Z" fill="#58a6ff"/>
+    <path d="M 0 -18 L 16 0 L 0 0 Z" fill="#79c0ff"/>
+    <path d="M -16 0 L 0 -18 L 0 0 Z" fill="#1f6feb"/>
+    <path d="M 0 22 L 16 0 L 0 0 Z" fill="#1f6feb" opacity="0.7"/>
+  </g>
 </svg>