refactor: replace generic catalog DTOs with shape-typed DTOs for type safety

Replace the single CatalogMaterialDto + CatalogDimensionsDto (bag of nullable
fields) with per-shape DTOs that have strongly-typed dimension properties.
Catalog JSON now groups materials by shape key instead of a flat array.
Delete the old SeedController/SeedDataDtos (superseded by CatalogService).
Scraper updated to emit the new grouped format, resume by default, and
save items incrementally.

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

CutList.Web/Data/SeedData/alro-catalog.json

@@ -27,5 +27,16 @@
       "isDefault": false
     }
   ],
-  "materials": []
+  "materials": {
+    "angles": [],
+    "channels": [],
+    "flatBars": [],
+    "iBeams": [],
+    "pipes": [],
+    "rectangularTubes": [],
+    "roundBars": [],
+    "roundTubes": [],
+    "squareBars": [],
+    "squareTubes": []
+  }
 }