feat(admin): /admin/material-files lists files in the material volume

app/admin.py

@@ -1,15 +1,35 @@
 import csv
 import io
+from pathlib import Path
 
 from fastapi import APIRouter, Depends, Query
 from fastapi.responses import Response
 
+from app.config import get_settings
 from app.db import list_leads, stats
 from app.security import require_admin
 
 router = APIRouter(prefix="/admin", tags=["admin"])
 
 
+@router.get("/material-files")
+def admin_material_files(_user: str = Depends(require_admin)):
+    """Lista los archivos en el directorio material/ con sus tamaños."""
+    material_dir = Path(get_settings().material_dir)
+    if not material_dir.exists():
+        return {"material_dir": str(material_dir), "exists": False, "files": []}
+    files = []
+    for path in sorted(material_dir.iterdir()):
+        if path.is_file():
+            size = path.stat().st_size
+            files.append({
+                "name": path.name,
+                "size_bytes": size,
+                "size_mb": round(size / (1024 * 1024), 2),
+            })
+    return {"material_dir": str(material_dir), "exists": True, "files": files}
+
+
 @router.get("/leads.json")
 def admin_leads_json(
     _user: str = Depends(require_admin),