feat: replace base64 I/O with GoFile.io URL upload/download

Remove colmap_workspace_b64 input in favour of colmap_workspace_url only.
Download workspaces from GoFile.io via gofile_downloader, plain URLs via
urllib. Upload output PLY/SPLAT to GoFile.io and return download-page URLs
instead of base64-encoded blobs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fix: rename --total-steps to --total-train-iters for current Brush CLI

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fix: fixture now has colmap/ prefix and correct sparse/0/ structure

- Archive extracts as colmap/images/ + colmap/sparse/0/ (handler needs colmap/ prefix)
- Pick largest COLMAP component so undistorter gets all 51 frames, not just 2

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fix: point smoke test fixture to v0.2.2 with correct sparse/0/ structure

Previous fixture had sparse/*.bin flat (image_undistorter output);
Brush requires sparse/0/cameras.bin etc.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

feat: add colmap_workspace_url input and real smoke test fixture

Replace the empty smoke test (which always errored) with a real
500-step test using the lighthouse fixture uploaded to v0.2.1 release.
handler.py now accepts colmap_workspace_url as an alternative to the
large base64 blob input.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fix: .runpod/test.json CUDA version 12.5 minimum

chore: add runpod badge

chore: add tests.json and expand hub.json GPU support

Adds required .runpod/tests.json for RunPod Hub automated endpoint
validation. Also expands gpuIds to include AMPERE_24/48 alongside ADA
variants and restores the shorter title.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Merge pull request #1 from alx/remove-runpod-tests

chore: remove runpod tests configuration

ci: switch cache to per-variant registry cache, add release body

- Replace type=gha with type=registry per CUDA variant (matches
  colmap-serverless pattern, survives GHA cache eviction)
- Add cache-to for cuda12.4 variant (was missing)
- Add release body with docker pull instructions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>