…e models

Extends the upscaling tab to support FLUX.1 and Z-Image models in addition
to the existing SD1.5/SDXL support. Each model architecture gets its own
tiled denoise backend node and frontend graph builder that handles the
architecture-specific denoising pipeline (transformer vs UNet), text
conditioning, VAE, ControlNet, and scheduler.

Backend:
- Add TiledFluxDenoiseLatents node with FLUX transformer tiling, ControlNet
  cropping (InstantX/XLabs), LoRA and scheduler support
- Add TiledZImageDenoiseLatents node with Z-Image transformer tiling,
  ZImageControlNet cropping, LoRA and scheduler support

Frontend:
- Add buildFluxMultidiffusionUpscaleGraph and
  buildZImageMultidiffusionUpscaleGraph graph builders
- Update useEnqueueUpscaling to dispatch correct graph per model base
- Update readiness validation for FLUX/Z-Image specific requirements
- Show model-appropriate scheduler (FLUX/Z-Image/SD) in upscale tab
- Show Z-Image VAE/Qwen3 selectors in upscale advanced settings
- Fix UpscaleWarning auto-select to also match "union" ControlNet names
- Reuse existing i18n keys for validation messages