Extract season overview/workflow cards and add sponsor seed data

Splits AdminSeasonsView into AdminSeasonOverviewCard and AdminSeasonWorkflowCard
for cleaner separation of concerns. Adds SeedSponsorsBootstrapper with demo
sponsor SVG assets and extends SeedCatalog with sponsor seed entries.

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

frontend/public/demo/sponsors/chibicanvas-market.svg

@@ -0,0 +1,17 @@
+<svg width="512" height="512" viewBox="0 0 512 512" fill="none" xmlns="http://www.w3.org/2000/svg">
+  <rect width="512" height="512" rx="124" fill="url(#bg)"/>
+  <rect x="118" y="152" width="276" height="220" rx="48" fill="#FFF7ED"/>
+  <path d="M188 152C188 114.444 218.444 84 256 84C293.556 84 324 114.444 324 152" stroke="#FFF7ED" stroke-width="22" stroke-linecap="round"/>
+  <path d="M178 222H334" stroke="#FB7185" stroke-width="18" stroke-linecap="round"/>
+  <path d="M178 270H334" stroke="#F59E0B" stroke-width="18" stroke-linecap="round"/>
+  <path d="M178 318H286" stroke="#8B5CF6" stroke-width="18" stroke-linecap="round"/>
+  <circle cx="336" cy="318" r="28" fill="#22C55E"/>
+  <path d="M324 318L334 328L350 308" stroke="#FFF7ED" stroke-width="10" stroke-linecap="round" stroke-linejoin="round"/>
+  <defs>
+    <linearGradient id="bg" x1="78" y1="58" x2="438" y2="450" gradientUnits="userSpaceOnUse">
+      <stop stop-color="#4C1D95"/>
+      <stop offset="0.52" stop-color="#C026D3"/>
+      <stop offset="1" stop-color="#FB7185"/>
+    </linearGradient>
+  </defs>
+</svg>