Migrate documentation to Mintlify and configure 301 redirects (#15502)

## Summary
Completes the migration of all documentation from twenty-website to a
new Mintlify-powered documentation site at docs.twenty.com.

## Changes Made

### New Package: `twenty-docs`
- ✅ Created new Mintlify documentation package
- ✅ Migrated 95 content pages (user-guide, developers, twenty-ui)
- ✅ Migrated 81 images
- ✅ Converted all custom components to Mintlify native components
- ✅ Configured navigation with 2 tabs and 94 pages
- ✅ Added Helper AI Agent with searchArticles tool for docs search

### Updated: `twenty-website`
- ✅ Added 11 redirect rules (301 permanent) in next.config.js
- ✅ Removed all documentation content (111 files)
- ✅ Removed documentation routes (user-guide, developers, twenty-ui)
- ✅ Removed documentation components (9 files)
- ✅ Updated keystatic.config.ts
- ✅ Preserved all marketing/release pages

### Updated: Core Files
- ✅ Updated README.md - docs links point to docs.twenty.com
- ✅ Updated CONTRIBUTING.md - code quality link updated
- ✅ Updated SupportDropdown.tsx - user guide link updated
- ✅ Updated Footer.tsx - user guide link updated

packages/twenty-website/src/shared-utils/constructSections.tsx

@@ -1,26 +0,0 @@
-import { type DocsArticlesProps } from '@/content/user-guide/constants/getDocsArticles';
-
-export const constructSections = (
-  docsArticleCards: DocsArticlesProps[],
-  isSection: boolean,
-): { name: string; info: string }[] => {
-  if (isSection) {
-    return [
-      {
-        name: docsArticleCards[0]?.topic,
-        info: docsArticleCards[0]?.sectionInfo,
-      },
-    ];
-  } else {
-    return Array.from(
-      new Map(
-        docsArticleCards
-          .filter((guide) => guide.numberOfFiles > 0)
-          .map((guide) => [guide.section, guide]),
-      ).values(),
-    ).map((guide) => ({
-      name: guide.section,
-      info: guide.sectionInfo,
-    }));
-  }
-};

packages/twenty-website/src/shared-utils/fetchArticleFromSlug.ts

@@ -1,6 +0,0 @@
-import { getPost } from '@/app/_server-utils/get-posts';
-
-export async function fetchArticleFromSlug(slug: string, basePath: string) {
-  const effectiveSlug = slug && slug.length > 0 ? slug : 'home';
-  return await getPost(effectiveSlug, basePath);
-}

packages/twenty-website/src/shared-utils/filterDocsIndex.tsx

@@ -1,11 +0,0 @@
-import { type DocsArticlesProps } from '@/content/user-guide/constants/getDocsArticles';
-
-export const filterDocsIndex = (
-  docsIndex: DocsArticlesProps[],
-  sectionName: string,
-): DocsArticlesProps[] => {
-  return docsIndex.filter(
-    (guide) =>
-      guide.section.includes(sectionName) && guide.title.includes(guide.topic),
-  );
-};

packages/twenty-website/src/shared-utils/getCardPath.tsx

@@ -1,35 +0,0 @@
-import { type DocsArticlesProps } from '@/content/user-guide/constants/getDocsArticles';
-
-export const getCardPath = (
-  card: DocsArticlesProps,
-  basePath: string,
-  isSection: boolean,
-  sectionName?: string,
-) => {
-  const isPlayground = [
-    'core-api-rest',
-    'metadata-api-rest',
-    'core-api-graphql',
-    'metadata-api-graphql',
-  ];
-
-  if (isPlayground.includes(card.fileName)) {
-    const apiType = card.fileName.includes('rest') ? 'rest-api' : 'graphql';
-    const apiName = card.fileName.includes('core') ? 'core' : 'metadata';
-    return `/developers/${apiType}/${apiName}`;
-  } else if (card.fileName.includes('storybook')) {
-    return 'https://storybook.twenty.com';
-  } else if (card.fileName.includes('components')) {
-    return `/twenty-ui`;
-  } else {
-    if (sectionName) {
-      return card.numberOfFiles > 1
-        ? `${basePath}section/${sectionName}/${card.fileName}`
-        : `${basePath}${card.fileName}`;
-    } else {
-      return card.numberOfFiles > 1 && !isSection
-        ? `${basePath}/section/${card.fileName}`
-        : `${basePath}/${card.fileName}`;
-    }
-  }
-};

packages/twenty-website/src/shared-utils/getSectionIcons.tsx

@@ -1,27 +0,0 @@
-import {
-  IconBook,
-  IconCode,
-  IconComponents,
-  IconGitPullRequest,
-  IconTool,
-} from '@tabler/icons-react';
-
-import { Theme } from '@/app/_components/ui/theme/theme';
-
-export const getSectionIcon = (section: string): JSX.Element => {
-  const iconSize = Theme.icon.size.md;
-
-  const sectionIcons: Record<string, JSX.Element> = {
-    'Getting started': <IconCode size={iconSize} />,
-    Contributing: <IconGitPullRequest size={iconSize} />,
-    Extending: <IconTool size={iconSize} />,
-    Components: <IconComponents size={iconSize} />,
-    Developers: <IconCode size={iconSize} />,
-  };
-  for (const key of Object.keys(sectionIcons)) {
-    if (section.includes(key)) {
-      return sectionIcons[key];
-    }
-  }
-  return <IconBook size={iconSize} />;
-};