fix(maps): split combined Indiana/Michigan entry into separate states

The East North Central region had a single "indianamichigan" entry pointing
to a pmtiles file that doesn't exist. Indiana and Michigan are separate
files in the maps repo.

Closes #350

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

Author: 2 people

collections/maps.json

@@ -367,11 +367,19 @@
           "size_mb": 400
         },
         {
-          "id": "indianamichigan",
+          "id": "indiana",
           "version": "2025-12",
-          "title": "Indianamichigan",
-          "description": "Topographic maps for the state of Indianamichigan",
-          "url": "https://github.com/Crosstalk-Solutions/project-nomad-maps/raw/refs/heads/master/pmtiles/indianamichigan_2025-12.pmtiles",
+          "title": "Indiana",
+          "description": "Topographic maps for the state of Indiana",
+          "url": "https://github.com/Crosstalk-Solutions/project-nomad-maps/raw/refs/heads/master/pmtiles/indiana_2025-12.pmtiles",
+          "size_mb": 400
+        },
+        {
+          "id": "michigan",
+          "version": "2025-12",
+          "title": "Michigan",
+          "description": "Topographic maps for the state of Michigan",
+          "url": "https://github.com/Crosstalk-Solutions/project-nomad-maps/raw/refs/heads/master/pmtiles/michigan_2025-12.pmtiles",
           "size_mb": 400
         },
         {