feat: automated Qdrant sync with Mistral embeddings + Kabelhandbuch ingestion

- Switch embedding API from OpenRouter to Mistral mistral-embed (1024-dim, EU/DSGVO)
- Add afterChange/afterDelete hooks to Posts.ts and Pages.ts for live sync
- Integrate kabelhandbuch.txt parsing into /api/sync-qdrant boot route
- Add .gitignore entries for kabelhandbuch.txt

.gitignore

@@ -32,4 +32,7 @@ backups/
 .env
 
 # Payload CMS auto-generated
-app/(payload)/admin/importMap.js
+app/(payload)/admin/importMap.js
+
+# Knowledge base source files
+kabelhandbuch.txt