Refactor experiences data format from JSON to Markdown

- Updated content.config.ts to change experiences source from JSON to Markdown files.
- Deleted JSON files for experiences: artdanjproduction, erisium, picard, and sevetys.
- Created corresponding Markdown files for each experience with structured front matter.
- Added new API endpoints for fetching experiences and projects in Markdown format.
- Removed unused ping API endpoint.
- Updated package.json with new dependencies for AI SDK and Zod.
- Added new resume files in PDF format for M1 2026 in English and French.

server/api/projects.get.ts

@@ -0,0 +1,10 @@
+import { queryCollection } from '@nuxt/content/server'
+
+export default defineCachedEventHandler(async (event) => {
+  return await queryCollection(event, 'projects')
+    .where('extension', '=', 'md')
+    .all()
+}, {
+  name: 'projects-list',
+  maxAge: 3600 // 1 hour
+})