refactor: remove unused imports

[YDX-2147483647]

This PR removes unused imports in TS/TSX files.

I noticed them when developing #294, and enabled the rule noUnusedImports | Biome locally.

noUnusedImports raises warnings in biome v2 by default. In biome v1, it is supported, but emits nothing by default.
I guess v1 hadn't implemented the rule well at that time, so it wasn't enabled by default.

I suggest upgrading to biome v2, but that would be a huge PR. It's best to have it done by a typst-jp member later (when you have time).

[Copilot]

Pull Request Overview

This PR removes unused imports from TypeScript/TSX files to improve code cleanliness and follows best practices by eliminating dead code. The changes were identified using Biome's noUnusedImports rule and prepare the codebase for potential future upgrades to Biome v2.

• Removed unused type imports (Body type)
• Removed unused component imports (SiteTitle)
• Removed unused utility function imports (type2href, FunctionDefinition, FunctionParameters)
• Removed unused metadata imports (githubOrganizationUrl)

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
website/src/index.tsx	Removed unused Body type import
website/src/components/ui/common/SideNavigation.tsx	Removed unused SiteTitle component import
website/src/components/ui/common/Footer.tsx	Removed unused githubOrganizationUrl import
website/src/components/templates/TypeTemplate.tsx	Removed unused type2href utility function import
website/src/components/templates/GroupTemplate.tsx	Removed unused FunctionDefinition and FunctionParameters component imports

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