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- Removed outdated Mintlify configuration files and documentation.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/source.config.ts

@@ -0,0 +1,27 @@
+import {
+  defineConfig,
+  defineDocs,
+  frontmatterSchema,
+  metaSchema,
+} from 'fumadocs-mdx/config';
+
+// You can customise Zod schemas for frontmatter and `meta.json` here
+// see https://fumadocs.dev/docs/mdx/collections
+export const docs = defineDocs({
+  dir: 'content/docs',
+  docs: {
+    schema: frontmatterSchema,
+    postprocess: {
+      includeProcessedMarkdown: true,
+    },
+  },
+  meta: {
+    schema: metaSchema,
+  },
+});
+
+export default defineConfig({
+  mdxOptions: {
+    // MDX options
+  },
+});