Clarify tutorial licensing and complete third-party attribution

[jxudata]

The tutorial's CC BY 4.0 statement previously excluded all software/code, and the Iris explorer lacked the dataset's formal citation and license. Original tutorial code is now offered under CC BY 4.0 or Apache 2.0, at the user's choice; original prose, diagrams, and notebook narrative remain under CC BY 4.0. This preserves the Apache option while making original code available under the tutorial's content license.

Changes:

• Synchronize the root and standalone materials license declarations. Retain separate third-party terms and exclude Affirm names and logos from the original-material license grants.
• Add Fisher's Iris citation, DOI, CC BY 4.0, and an explanation of record selection, numeric species encoding, and withheld query labels to the notices, explorer README, source, and visible tutorial copy.
• Publish complete original license texts for the installed Svelte/SvelteKit and D3 dependency graph (38 packages), Three.js r160, Inter, JetBrains Mono, Jersey 10, and Transformer Explainer. Distinguish bundled libraries from CDN-loaded libraries and fonts.
• Copy third-party notices into the deployed website and add a footer link, so the Pages distribution carries the notices as well as the repository. This browser inventory does not claim to cover every development or notebook dependency.
• Place the README's interactive website link on its own bold line.

Validation:

• Root/materials license and notice copies are byte-identical; the website notice matches the canonical third-party notice. Relative README links and git diff checks pass.
• Svelte check reports zero errors and warnings; static build passes, with existing dependency warnings.
• Browser checks at 375, 768, 1024, and 1440px show the notices link and no horizontal page overflow. All seven notice/license resources return HTTP 200 after the build, and Iris citation text is visible.
• Apache and the upstream interface MIT license remain unchanged. No inference or model changes; the only source-code edit is an attribution comment.