docs: README diagrams reference deleted image files

**Describe the bug**

Both `README.md` and `README.zh_CN.md` embed two diagram paths that no longer exist on `main`:

- `.github/static/img/eino/eino_concept.jpeg`
- `.github/static/img/eino/eino_framework.jpeg`

As a result, the concept and framework diagrams render as broken images on the repository landing page and in the Chinese README.

**To Reproduce**

1. Open either README on the current `main` branch.
2. Inspect the diagram below the introduction and the diagram in the "Eino Framework Structure" section.
3. Observe that both image requests return HTTP 404.

The old JPEGs were deleted when the tracked PNG diagrams were introduced. The current replacements are:

- `.github/static/img/eino/eino_project_structure_and_modules.png`
- `.github/static/img/eino/eino_architecture_overview.png`

**Expected behavior**

Both README variants should reference tracked images so all diagrams render.

**Screenshots**

Not applicable; the two old raw-content URLs return 404, while both replacement PNG URLs return 200.

**Version:**

`main` at `ebd616c8291e957684ea6ca99dd54225d04e0438`

**Environment:**

GitHub README rendering and a clean local checkout.

**Additional context**

I checked open and closed issues, pull requests in every state, repository discussions, and the files changed by every currently open PR. PR #1176 edits the same README files but only fixes badge links; it does not update these image references.

Open README.md and README.zh_CN.md and locate the two diagram references below the introduction and in the "Eino Framework Structure" section. Replace the deleted JPEG paths with the tracked PNG paths named in the issue, then verify both README variants render all diagrams and the referenced image URLs no longer return 404.

Written by the indexing model from the issue text.