runpod: let the operator state a model's size instead of estimating it

weights_gb, on the model entry or its runpod block, is taken as-is and the
HuggingFace estimate is skipped. It is the only honest answer for a URL
download, an upload or a local file — none of which the estimator can see —
and for an HF repo it beats a heuristic that deliberately errs high (SDXL:
estimated 35 GB, actually ~7 for one precision). A nonsense value is ignored
rather than trusted, and the field is never seeded to a pod: it describes the
pod's disk, not the model.

/v1/models/test/state now reports the disk a pod would be rented with, the
weight size used, and whether that size was stated or estimated — decided
before any money is spent.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0182DhR1eFNPQyGmDrpHbedY