fix: enable gradients for texture baking in GLB export

- Removed @torch .no_grad() from generate_renderings to allow gradients for texture baking
- Added torch.no_grad() context managers around video rendering to save memory
- This fixes 'element 0 of tensors does not require grad' error during GLB export

app.py

@@ -471,7 +471,6 @@ def load_slat_file(
 
 
 @_gpu(duration=600)
-@torch.no_grad()
 def generate_renderings(
     asset_state: Dict[str, Any],
     hdri_file_obj: Any,
@@ -519,32 +518,34 @@ def generate_renderings(
 
     # ── Render videos ──────────────────────────────────────────────────
     progress(0.12, desc="Rendering camera-orbit video…")
-    cam_frames = pipe.render_camera_path_video(
-        slat, hdri_np,
-        num_views=int(num_cam),
-        fov=float(fov), radius=float(radius),
-        hdri_rot_deg=float(hdri_rot),
-        full_video=True,
-        shadow_video=True,
-        bg_color=(1, 1, 1),
-        verbose=True,
-    )
+    with torch.no_grad():
+        cam_frames = pipe.render_camera_path_video(
+            slat, hdri_np,
+            num_views=int(num_cam),
+            fov=float(fov), radius=float(radius),
+            hdri_rot_deg=float(hdri_rot),
+            full_video=True,
+            shadow_video=True,
+            bg_color=(1, 1, 1),
+            verbose=True,
+        )
     p_cam = session_dir / "video_camera_orbit.mp4"
     imageio.mimsave(p_cam, cam_frames, fps=int(fps))
     del cam_frames
     _free_cuda()  # Free GPU mem temporarily while still in same CUDA context
 
     progress(0.55, desc="Rendering HDRI-rotation video…")
-    roll_frames, hdri_frames = pipe.render_hdri_rotation_video(
-        slat, hdri_np,
-        num_frames=int(num_hdri),
-        yaw_deg=float(yaw), pitch_deg=float(pitch),
-        fov=float(fov), radius=float(radius),
-        full_video=True,
-        shadow_video=True,
-        bg_color=(1, 1, 1),
-        verbose=True,
-    )
+    with torch.no_grad():
+        roll_frames, hdri_frames = pipe.render_hdri_rotation_video(
+            slat, hdri_np,
+            num_frames=int(num_hdri),
+            yaw_deg=float(yaw), pitch_deg=float(pitch),
+            fov=float(fov), radius=float(radius),
+            full_video=True,
+            shadow_video=True,
+            bg_color=(1, 1, 1),
+            verbose=True,
+        )
     p_hdri = session_dir / "video_hdri_rotation.mp4"
     p_roll = session_dir / "video_env_roll.mp4"
     imageio.mimsave(p_hdri, hdri_frames, fps=int(fps))