Refactor documentation structure and dependencies for migration to Fumadocs

- Updated `.gitignore` to include new build and generated content directories.
- Removed outdated Mintlify configuration files and documentation.
- Introduced new `MIGRATION.md` to outline the transition from Mintlify to Fumadocs.
- Added `mdx-components.tsx` for MDX component configuration and compatibility.
- Updated `package.json` and `next.config.mjs` for new dependencies and Next.js configuration.
- Created `source.config.ts` for content source configuration.
- Added OpenAPI specification in `openapi.json` for API documentation.
- Removed legacy files and adjusted project structure to align with Fumadocs conventions.

docs/mdx-components.tsx

@@ -0,0 +1,39 @@
+import defaultMdxComponents from 'fumadocs-ui/mdx';
+import type { MDXComponents } from 'mdx/types';
+import {
+  Frame,
+  CardGroup,
+  MintlifyCard,
+  Steps,
+  Step,
+  Tip,
+  Note,
+  Warning,
+  Info,
+  Danger,
+  AccordionGroup,
+  Accordion,
+} from '@/components/mintlify-compat';
+import { APIPage } from '@/components/api-page';
+
+export function getMDXComponents(components?: MDXComponents): MDXComponents {
+  return {
+    ...defaultMdxComponents,
+    // Mintlify compatibility components
+    Frame,
+    CardGroup,
+    Card: MintlifyCard,
+    Steps,
+    Step,
+    Tip,
+    Note,
+    Warning,
+    Info,
+    Danger,
+    AccordionGroup,
+    Accordion,
+    // OpenAPI component
+    APIPage,
+    ...components,
+  };
+}