docs: verify Open WebUI AceDataCloud integration

[acedatacloud-dev]

Summary

• Publish independent English and Chinese Open WebUI onboarding pages and navigation.
• Document the tested Open WebUI v0.11.4 UI: External connection, Bearer token, https://api.acedata.cloud/v1, Chat Completions, model discovery, optional Model IDs allowlist, and chat verification.
• Explain that Open WebUI's title, tag, and follow-up generation can make additional billable requests.

Validation

• Ran the official Open WebUI v0.11.4 Docker image (ghcr.io/open-webui/open-webui:v0.11.4, digest sha256:9591b13f13843c7721c2b8eaf7382846c81b3ffe126526d1888d1fed50c6a33f) in a local isolated instance. Added the AceDataCloud connection in the real admin UI.
• Valid API token returned 107 models from /v1/models; Open WebUI model selector displayed them. A manually added gpt-4o-mini Model ID changed the connection to an allowlist. An invalid token returned 401 invalid_token for both /v1/models and /v1/chat/completions.
• Sent Reply with only ADC_OPEN_WEBUI_OK. through the real Open WebUI chat UI using gpt-4o-mini; the saved chat returned ADC_OPEN_WEBUI_OK. Matched the main streaming request to a 200 usage record, 3,981 tokens, and 0.0011376062712 Credits charged. The same chat triggered three separate title/follow-up/tag requests; the four matched records totaled 0.0013967466219 Credits. No secret or request payload is included in this PR.
• npm test: 48 Python and 4 Node tests passed. node scripts/validate_mdx.mjs .: 4,129/4,129 pages passed syntax and local-link checks. git diff --check passed.

Publication and maintenance

• This PR is independent of draft Docs docs: add n8n, Dify, GitLab, and Open WebUI onboarding #109 and should be merged once reviewed. After merge, verify the Mintlify English and Chinese URLs and navigation. Update the UI labels and model examples when Open WebUI or the AceDataCloud catalog changes.
• The official Open WebUI OpenAI-compatible provider guide is the current discoverable entry point for this generic connection type. An upstream community tutorial and catalog entry were submitted as open-webui/docs #1453. A maintainer closed that PR without merging or leaving an explanation, so AceDataCloud is not listed in the official Open WebUI documentation. The generic OpenAI-compatible provider guide remains the official discoverable entry point. This PR does not validate tools, images, or files.