Release staging to main - 2026-05-19

[suguanYang]

Summary

• Release the current staging tree to main.
• Includes the architecture refactor and cleanup work that deepens API, worker, retrieval, job lifecycle, parser, webhook, demo, and packaging module boundaries.
• Includes follow-up fixes for MinerU upload-mode configuration, Python 3.14 dependency support, retrieval VLM image selection, empty-query retrieval response serialization, and configurable PDF page limits.
• Includes security/code-quality cleanup from the staging hardening pass.

Notes

• This release branch resolves the duplicated-history conflict between staging and main while preserving the exact tracked file tree from origin/staging.

Verification

• The release branch tree matches origin/staging.
• git diff --check --cached passed before the release merge commit.
• Release PR CI should be treated as the final merge gate.