docs: add Sebastian Software README branding

[agent-werner]

Adds a consistent Sebastian Software brand badge near the existing README badge/header area and a shared footer linking to https://oss.sebastian-software.com.\n\nThis keeps the open-source project READMEs visually aligned across the organization while preserving each README's existing structure.\n\nFollow-ups applied from review:\n- Badge placement now follows each project's existing badge/header layout.\n- Footer separator has a blank line before it.\n- Links target the .com OSS site for the English version.\n- Footer copyright years are mapped from the relevant project history: 2026.\n- Footer logo uses the hosted Sebastian Brand asset.

[greptile-apps]

Greptile Summary

This PR adds a brand badge after the # python2ts title and an HTML footer block (logo + copyright) consistent with other Sebastian Software OSS repositories. The previously flagged setext-heading issue (--- promoting the license line to <h2>) is resolved: two blank lines now precede the horizontal rule.

Confidence Score: 5/5

Documentation-only change with no logic impact; safe to merge.

No P0/P1 findings. The only prior concern (setext heading) was already addressed. The changes are purely cosmetic Markdown/HTML additions.

No files require special attention.

Important Files Changed

Filename	Overview
README.md	Adds a "Powered by Sebastian Software" badge near the top and an HTML footer block with logo and copyright; the setext-heading issue from the prior review has been resolved with blank lines before the --- separator.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["README.md top"] --> B["# python2ts heading"]
    B --> C["[![Powered by Sebastian Software] badge (NEW)"]
    C --> D["...existing content..."]
    D --> E["## License\nMIT © Sebastian Software GmbH"]
    E --> F["blank lines (NEW)"]
    F --> G["--- separator (NEW)"]
    G --> H["<!-- sebastian-software-branding:start --> (NEW)"]
    H --> I["Logo + OSS link"]
    I --> J["Copyright 2026"]
    J --> K["<!-- sebastian-software-branding:end --> (NEW)"]

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[agent-werner]

@greptileai I addressed the README branding feedback in the latest force-push: added spacing before the horizontal rule, switched OSS links to https://oss.sebastian-software.com, mapped the footer copyright year(s) from the relevant project history, and moved the logo to the hosted Sebastian Brand asset. Could you please re-review?