docs: add draw.io diagrams and neutralize readme

[falltwo]

Summary

• replace Mermaid and legacy PNG diagrams with editable draw.io architecture and procurement-flow diagrams in Chinese and English
• apply standard flowchart symbols and consistent top-to-bottom routing
• revise README wording to a neutral, scope-oriented tone
• remove the superseded legacy architecture and governance-flow images
• add public v0.1 release notes and version links for the initial cleaned snapshot

Verification

• current branch: python -m pytest -q — 327 passed
• v0.1 public snapshot (a096962): python -m pytest -q — 56 passed
• draw.io validation: 0 errors, 0 warnings, 0 crossings, 0 overlaps on all four diagrams
• final PNG verification: strict decode passed and embedded draw.io metadata present
• README local-link and public-document scans passed