[TOOL-4831] SDK: Fix MediaRenderer not showing poster for 3d models (#7387)

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## PR-Codex overview
This PR focuses on fixing the display of the `poster` in the `MediaRenderer` component for 3D models and adding tests to ensure expected behavior.

### Detailed summary
- Updated the `MediaRenderer` component to show a `poster` image for 3D models.
- Added a new test case to verify rendering of the `poster` image when a 3D model is provided.
- Replaced hardcoded image URL with a constant `imageLink` for clarity in tests.

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<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **Bug Fixes**
	- Fixed an issue where the poster image was not displayed when rendering 3D models in the MediaRenderer component. Now, if a poster image is available, it will be shown as a fallback for unsupported 3D models.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: MananTank

.changeset/heavy-ghosts-nail.md

@@ -0,0 +1,5 @@
+---
+"thirdweb": patch
+---
+
+Fix `poster` not shown in `MediaRenderer` component for 3D models

packages/thirdweb/src/react/web/ui/MediaRenderer/MediaRenderer.test.tsx

@@ -14,6 +14,11 @@ import {
   mergeRefs,
 } from "./MediaRenderer.js";
 
+const three3dModelLink =
+  "https://i2.seadn.io/matic/0x2953399124f0cbb46d2cbacd8a89cf0599974963/bd1801876c5cf1302484e225c72959/49bd1801876c5cf1302484e225c72959.glb";
+const imageLink =
+  "https://i.seadn.io/gae/r_b9GB0iYA39ichUlKdFLeG4UliK7YXi9SsM0Xdvm6pNDChYbN5E7Fxop1MdJCbmNvSlbER73YiA9WY1JbhEfkuIktoHfN9UlEZy4A?auto=format&dpr=1&w=1000";
+
 describe("MediaRenderer", () => {
   it("should render nothing if no src provided", () => {
     render(<MediaRenderer client={TEST_CLIENT} />);
@@ -27,14 +32,9 @@ describe("MediaRenderer", () => {
     }, 1000);
   });
 
-  it("should render a plain image", () => {
-    render(
-      <MediaRenderer
-        client={TEST_CLIENT}
-        src="https://i.seadn.io/gae/r_b9GB0iYA39ichUlKdFLeG4UliK7YXi9SsM0Xdvm6pNDChYbN5E7Fxop1MdJCbmNvSlbER73YiA9WY1JbhEfkuIktoHfN9UlEZy4A?auto=format&dpr=1&w=1000"
-      />,
-    );
-    waitFor(() => {
+  it("should render a plain image", async () => {
+    render(<MediaRenderer client={TEST_CLIENT} src={imageLink} />);
+    await waitFor(() => {
       expect(screen.getByRole("img")).toBeInTheDocument();
     });
   });
@@ -222,4 +222,17 @@ describe("MediaRenderer", () => {
       expect(iframe).toHaveAttribute("src", "https://example.com/video");
     });
   });
+
+  it("should render poster image for 3d models", async () => {
+    render(
+      <MediaRenderer
+        client={TEST_CLIENT}
+        src={three3dModelLink}
+        poster={imageLink}
+      />,
+    );
+    await waitFor(() => {
+      expect(screen.getByRole("img")).toBeInTheDocument();
+    });
+  });
 });

packages/thirdweb/src/react/web/ui/MediaRenderer/MediaRenderer.tsx

@@ -111,6 +111,21 @@ export const MediaRenderer = /* @__PURE__ */ (() =>
         console.error(
           "Encountered an unsupported media type. 3D model support was removed in v5.92.0. To add a 3D model to your app, use @google/model-viewer and use the ModelViewer component.",
         );
+
+        // show poster
+        if (possiblePosterSrc.mimeType?.startsWith("image/")) {
+          return (
+            <ImageRenderer
+              style={mergedStyle}
+              src={possiblePosterSrc.url}
+              alt={alt}
+              ref={ref as unknown as React.ForwardedRef<HTMLImageElement>}
+              className={className}
+              height={height}
+              width={width}
+            />
+          );
+        }
       }
 
       //  video