refactor: structure refactor and docs improvements.

[Daanvdplas]

Refactor:

• Structure of the website
• The toggle used for cc and pop-cli, pop-cli is now first because it is the tool with best devex. In addition, in the pages where possible contracts-ui is added.
• getting started page simplified, none of the info is removed, just moved or it was already covered somewhere else.
• moved anything related to building ink! contracts with solidity abi or other solidity contracts in dedicated section in the docs (removed ethereum tutorial and moved there too).

[Copilot]

Pull Request Overview

This PR performs a major documentation restructuring for ink! v6, reorganizing content into clearer categories and adding comprehensive Solidity interoperability documentation. The changes remove outdated tutorial content and establish a new "Ink & Solidity" section with detailed guides for using Ethereum tooling with ink! contracts.

Key Changes:

• Removes Ethereum Compatibility tutorial section and replaces it with comprehensive Solidity Interoperability documentation
• Restructures sidebar navigation from nested objects to flat arrays with categorized sections
• Adds new "Getting Started" testing guide and reorganizes advanced topics into separate sections
• Updates 200+ internal documentation links to reflect new file paths

Reviewed Changes

Copilot reviewed 52 out of 92 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tutorials/sidebar.js	Removed Ethereum Compatibility section
tutorials/ethereum-compatibility/*	Deleted outdated tutorial files (content replaced in docs/solidity-interop)
docs/solidity-interop/*	Added comprehensive guides for Solidity ABI, MetaMask, Hardhat, Wagmi integration, and type references
sidebars.js	Major restructuring: flattened structure, reorganized into clear sections (Basics, Advanced, Development, Reference)
docs/getting-started/testing.md	New guide for testing contracts
docs/reference/macros-attributes/*	Added documentation for all ink! macros and attributes
docs/advanced/*	Moved advanced topics (XCM, upgradeability, precompiles, environment, datastructures)
docs/development/*	Consolidated testing, debugging, linting, and verification documentation
Various link updates	Updated internal references to match new file structure

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[cmichi]

@Daanvdplas

Those two nav items are not recognizable as such, they should have the same style as the others.

[Daanvdplas]

Fixed the navigation bar @cmichi !

[Daanvdplas]

This content and below have been moved to a page Calling Solidity Contracts.

[davidsemakula]

Very nice!

I've left a few comments/suggestions below.

[Daanvdplas]

Closes #517