Add Uxify startup program

[shawnruan0218-code]

What changed

• Add the missing Uxify vendor record.
• Capture the $5,000 agent credits and ongoing 20% subscription discount.
• Model the published startup age, funding, and website requirements.

Closes #612

Sources

• https://uxify.com/startup-program/

Validation

• Pinned Sourcey Catalog Verifier: {"status":"valid","vendors":1,"programs":1,"offers":1}

Certification

• I changed only allowed repository content and did not mix vendor YAML with other paths.
• Public sources substantiate every submitted factual value; any Sourcey-written prose is a neutral summary, not a fabricated vendor quote.
• I did not author verification, provenance, freshness, or signature claims.
• My commits include a Signed-off-by line.

[auscaster]

Thanks for this. sourcey/validation is green, but the evidence pass for this head could not locate support for every submitted fact, so sourcey/admission cannot go green yet.

Uncovered on the record: /description, /category.

Fix it on this same branch: either cite a public page that states the fact (add the URL to sources and reference its source_id from the record that needs it), or change the record to what the cited pages do say. Push to the branch and the checks re-run automatically.