feat: export service — DOCX, PDF, MD generation and download API

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/schemas/export_file.py

@@ -0,0 +1,20 @@
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel
+
+from app.models.export_file import ExportFormat
+
+
+class ExportRequest(BaseModel):
+    format: ExportFormat
+
+
+class ExportFileResponse(BaseModel):
+    id: uuid.UUID
+    protocol_id: uuid.UUID
+    format: ExportFormat
+    file_size: int
+    created_at: datetime
+
+    model_config = {"from_attributes": True}