feat: Vercel Hobby deploy readiness — image URLs, jsonrepair, DeepSeek

- Move vercel.json to apps/web/ with correct route paths; cap scene route
  maxDuration 120→60s for Hobby. Root vercel.json removed. Vercel project's
  Root Directory must be set to apps/web (Deploy button URL passes this).
- Switch image transport from base64-in-JSON to Runware-hosted URLs:
  generateImage now uses outputType=URL and returns {imageUrl, imageUuid};
  StartResponse/SceneResponse carry imageUrl; VisionRequest carries
  prevImageUrl (server re-fetches the bytes for click annotation). This
  eliminates the 4.5MB serverless body-size risk.
- Painter and director prefer URL over UUID for referenceImages — the UUID
  returned by Runware imageInference isn't always recognized in the refs
  pipeline (surfaces as `failedToTransferImage`).
- Client preloads scene images via `new Image().decode()` before committing
  to React state, so URL transitions render instantly; prefetched scenes
  also warm the HTTP cache.
- jsonParser uses the jsonrepair package (replaces hand-rolled repair) and
  adds a targeted preRepair regex for the missing-key-close-quote pattern
  that jsonrepair couldn't disambiguate. Full raw model output dumped on
  failure for diagnostic visibility.
- Default text provider switched to DeepSeek v4-flash via direct API
  (significantly more stable JSON than MiMo v2.5-pro). VISION/TTS stay on
  MiMo (DeepSeek has no multimodal / TTS offerings).
- next.config: drop dead experimental.serverActions.bodySizeLimit (no
  server actions used).
- README: real Deploy button URL (zonghaoyuan/yume + root-directory=apps/web
  + TTS/MOCK_IMAGE in env list); refreshed env vars table with optional
  TTS section.

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

apps/web/components/PlayCanvas.tsx

@@ -159,7 +159,7 @@ function ChoiceButton({
 
 // ── Main component ─────────────────────────────────────────────────────
 export function PlayCanvas({
-  imageBase64,
+  imageUrl,
   audioBase64,
   audioMime,
   muted,
@@ -171,7 +171,7 @@ export function PlayCanvas({
   onSelectChoice,
   fullViewport = false,
 }: {
-  imageBase64: string | null;
+  imageUrl: string | null;
   audioBase64: string | null;
   audioMime: string | null;
   muted: boolean;
@@ -271,7 +271,7 @@ export function PlayCanvas({
     });
   }
 
-  const interactive = phase === "ready" && !!imageBase64;
+  const interactive = phase === "ready" && !!imageUrl;
   const dimmed = phase === "transitioning";
 
   const sizeStyle = fullViewport
@@ -306,16 +306,16 @@ export function PlayCanvas({
         />
       )}
 
-      {imageBase64 ? (
+      {imageUrl ? (
         <div
           className="relative inline-block"
           style={{ boxShadow: fullViewport ? "none" : SHADOW }}
         >
-          {/* Background image */}
+          {/* Background image — Runware CDN URL or data URI (mock mode) */}
           <img
-            key={imageBase64.slice(-48)}
+            key={imageUrl.slice(-48)}
             ref={imgRef}
-            src={`data:image/png;base64,${imageBase64}`}
+            src={imageUrl}
             alt="Generated scene"
             onClick={handleImageClick}
             onLoad={(e) => {