[Frankie-Xu]

Summary

• Add docs/external-services.md, the missing dependency guide already linked from README Quick Start and Additional Guides.
• Document service purpose, feature requirements, data sent to providers, and the actual API/worker example environment keys.
• Match current main configuration: default vision model deepseek-flash, optional ASSET_MODEL fallback to IMAGE_MODEL, DeepSeek credentials for default models, Qwen/DashScope overrides, and separate runtime/migration database roles. Remove the retired IMAGE_MODEL_MAX guide entry.
• Scope MinerU to standard V1 parsing, document the V2 Vision Page path and LibreOffice fallback, require both QStash callback signing keys, and describe retained GPT/Moesif configuration according to its actual runtime use.
• Align the README Quick Start provider-credential bullet with the shared client's model routing.
• Merged current main (f9d61119) normally, preserving the existing PR commit. The resulting PR adds the guide and corrects one README bullet; parser support, runtime defaults, and environment examples are unchanged.

Closes #333 (missing guide; HTML/HTM support is already documented on main).

Verification

• Reproduced the outdated guide's IMAGE_MODEL_MAX entry against current main examples, then verified the corrected guide's 77 environment keys all exist in API and/or worker examples. Keys described as shared occur in both examples; API-only keys are identified.
• Seven README/guide relative document links resolve in the tracked Git tree, including the previously missing guide.
• Default vision model, empty asset-model fallback, and migration/runtime roles were checked against current configuration/client source.
• git diff --check passed.
• Independent source/spec review completed before push.
• Documentation only; no account-backed model calls or runtime suite was required. Required GitHub Actions results are reported separately; pending fork workflow approval is not a passing CI result.

Deployment Notes

• No new or changed environment variables.
• No database migrations, queue changes, storage changes, or release-order requirements.
• Backwards compatible; rollback is reverting this PR's guide commits.

Checklist

• Tests were added or updated when behavior changed — N/A (documentation only)
• Public docs, examples, or OpenAPI contracts were updated when needed
• Database migrations are idempotent and safe to deploy — N/A
• Logs, errors, and validation paths avoid leaking secrets or user data — no credentials or private endpoints added
• The pull request description explains any breaking or user-visible change — none

[Frankie-Xu]

Please approve Actions workflows for this first-time fork PR (runs are sitting at action_required). No further code changes pending on this branch.

[Frankie-Xu]

Rebased onto current main (9489fa2c, includes #414/#415). .env.example keys are unchanged since the previous rebase; still waiting on first-time fork Actions workflow approval.

[EricNGOntos]

Appreciate the write-up. We're keeping external-services docs on a maintainer track for now so they stay in sync with what we actually ship — closing this rather than landing a standalone guide PR.