Fix ESRGAN model structure to match checkpoint exact state dict

Add Finegrain ESRGAN 4X endpoint

Async InvSR: POST returns job_id instantly, poll for result (fixes Swagger timeout)

Clean rewrite: fix _patch_invsr NameError, status tracking

Move InvSR download to runtime (avoids build OOM), add status endpoint

Pre-download SD-Turbo at build time, use snapshot_download for reliable caching

Add real InvSR model with CPU/float32 support (SD-Turbo + noise predictor)

InvSR endpoint auto-falls back to MewZoom 4X on CPU

Add Super-Resolution API: MewZoom 2X/4X + comparison + metrics