Fix Blender 5.2 texture readback corruption

[ThinkWithPbody]

Summary

• remove the unconditional NumPy transpose from Spout texture readback
• remove the same transpose from NDI texture readback
• preserve the existing is_flipped behavior

This fixes the diagonal/corrupted output reported with Blender 5.2, where the buffer returned by GPUTexture.read() already has the expected layout.

Fixes #63.

Validation

• python -m py_compile fbs/spout/SpoutServer.py fbs/ndi/NDIServer.py
• git diff --check
• manual Blender 5.2 testing confirmed correct output in Solid and EEVEE views

Cycles

We were unable to produce scene output from Cycles. The shared frame remained black except for viewport UI overlays, although Blender's own Cycles viewport rendered the scene. Camera movement updated the overlays, and changing exposure had no effect. This PR does not attempt to change the capture architecture or address that separate limitation.

Review note

This patch was produced using agentic coding with OpenAI Codex. Although the final code change is intentionally very small, it needs human review before merging.