Update Match3D/image-generation docs & code

Adds/updates documentation, assets and implementation for Match3D and puzzle image generation workflows. Key changes: decision logs and pitfalls updated to prefer VectorEngine Gemini for Match3D material sheets and to require edits (multipart) for 1:1 container reference images; guidance added for when to use APIMart vs VectorEngine. .env.example clarified APIMart/Responses config. Many new public assets and PPT visuals added. Code changes across frontend and backend: updated shared contracts, server-rs match3d/puzzle/image-generation handlers, VectorEngine/OpenAI image generation clients, and multiple React components/tests to handle UI/background/container image signing, edits workflow, and puzzle UI background resolution. Added src/services/puzzle-runtime/puzzleUiBackgroundSource.ts and related test updates. Includes notes about multipart HTTP/1.1 requirement and test/verification commands in docs.

src/components/rpg-entry/RpgEntryBrandLogo.tsx

@@ -18,7 +18,9 @@ export function RpgEntryBrandLogo({
       aria-hidden={decorative || undefined}
       aria-label={decorative ? undefined : '陶泥儿 GENARRATIVE'}
     >
-      <span className="platform-brand-logo__title">陶泥儿</span>
+      <span className="platform-brand-logo__title">
+        陶泥<span className="platform-brand-logo__title-suffix">儿</span>
+      </span>
       <span className="platform-brand-logo__subtitle">GENARRATIVE</span>
     </span>
   );