feat: new docs (#857)

<!-- CURSOR_SUMMARY -->
> [!NOTE]
> Restructures docs into a new Blockchain Platform with SDK docs, adds
site infra (AI chat, mermaid, image zoom, redirects), and refreshes
EVM/Fabric/Hedera content with unified assets.
> 
> - **Docs architecture**:
> - Introduce `blockchain-platform` as the new root (about, platform
components, supported chains, security, support, releases, terms), with
redirects from legacy paths.
> - Move legacy kit into `asset-tokenization-kit-legacy`; add Docker
sync for latest kit content/images.
> - Add first‑class `sdk/` docs (CLI + SDK modules) with generator + MDX
ingestion.
> - **Site platform (Next/Fumadocs)**:
> - Replace app/layout with new `(documentation)` routes, OG image, LLM
endpoints (`/llms.mdx`, `/llms-full.txt`), markdown negotiation proxy,
and SEO/meta updates.
> - New UI/MDX components: Mermaid, code blocks/tabs, accordion, steps,
files, image zoom, type tables, inline TOC, banner.
> - Add AI chat endpoint (`/api/chat`) and client trigger; PostHog kept.
> - Styling/config: Tailwind v4 preset, color tokens,
ESLint/PostCSS/tsconfig/next rewrites & redirects.
> - **Content updates**:
> - Refresh many EVM/Fabric/Hedera guides; unify images to
`/images/btp/...`; add new platform pages and release notes.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
f4783b3. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

<!-- This is an auto-generated description by cubic. -->
## Summary by cubic
Restructured the docs by introducing a new Blockchain Platform section
with SDK/dev-tools references and moving the Asset Tokenization Kit to a
dedicated legacy section. Cleaned up repo configs and updated ignores to
simplify maintenance.

- New Features
- Added Blockchain Platform docs with About page and SDK/dev-tools
snippets: Blockscout, CLI, EAS, Hasura, IPFS, MinIO, Portal, The Graph,
Viem.
- Created Asset Tokenization Kit (legacy) section with updated overview,
asset classes, use cases, and release notes.
- Moved blockchain-and-ai content under blockchain-platform and
refreshed related pages.

- Migration
- Update links: application-kits/asset-tokenization/... →
asset-tokenization-kit-legacy/...; about-settlemint/... →
blockchain-platform/about-settlemint/....
- asset-tokenization-kit and sdk content are now ignored by default
(kept via .gitkeep); adjust any scripts or links that referenced tracked
files.
- Local/editor/assistant configs and env files were removed (.claude,
.cursor, .vscode, CLAUDE.md, .env); add them locally if needed.
bunfig.toml and cli.json were added for tooling.

<sup>Written for commit 652a1e0.
Summary will update automatically on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

Author: roderik