feat(civitai): enrich base-model discovery with github constants

[CalamitousFelicitousness]

Pre-scriptum

I'm going to be honest; the only reason I wasted so much time on this is that I didn't feel like admitting defeat against the absolute misery that is Civitai API. At the end of this I'm utterly ambivalent whether you consider it worth the salt to even read this ridiculous contraption.

Description

CivitAI removed enum validation from /api/v1/models?baseModels=X (now returns 200 with empty items on unknown values), which left the base-model filter dropdown empty.

Notes

Fix in two parts.

1. Point the base_models discovery probe at /images instead of /models. /images still returns a ZodError with the full enum list (82 names at time of writing). The existing parser handles the shape unchanged.

2. Also fetch civitai/civitai's base-model.constants.ts from GitHub and merge per-name metadata (group, ecosystem, engine, family, hidden) into a new base_models_info field on the response. The live probe remains authoritative for which names exist; GitHub provides the metadata and doubles as a fallback name list if the probe comes back empty.

Backward compatible: the existing base_models list keeps the same shape. Clients that want grouped dropdowns, hidden-flag filtering, or image/video separation can consume base_models_info instead.

The GitHub fetch has a separate 6h cache since these constants change much less often than the probes it sits alongside.

[vladmandic]

ugly but valid. only feedback is to place into separate helper py file in modules/civitai to limit the bloat to client_civitai.py

a bit off-topic, here's a generic ts:const -> python:dict converter :)
extract_base_model_config.py