fix: preserve gameplay data and correct duel evaluation

- Preserve snake customizations across database migrations and merges.
- Lazily load optional storage backends for SQLite maintenance scripts.
- Match Apex territory and nearest-food tie-breaking semantics.
- Resolve duel occupancy after simultaneous movement and food growth.
- Recompute simulated head-to-head danger after body growth.
- Add regression coverage and declare the aiofiles dependency.

tests/test_MergeGameplayDatabases.py

@@ -27,10 +27,14 @@ class TestMergeGameplayDatabases(unittest.TestCase):
         90 if cleaned else None, "high" if cleaned else None,
         '["already_scored"]' if cleaned else None,
       ))
-      connection.execute(
-        "INSERT INTO game_snakes (game_id,snake_id,snake_name,is_you) VALUES (?,?,?,?)",
-        (game_id, "me", "PrismBattleSnake", 1),
-      )
+      connection.execute("""
+        INSERT INTO game_snakes (
+          game_id,snake_id,snake_name,is_you,customizations_json
+        ) VALUES (?,?,?,?,?)
+      """, (
+        game_id, "me", "PrismBattleSnake", 1,
+        '{"color":"#663399","head":"ferret","tail":"swirl"}',
+      ))
       connection.execute("""
         INSERT INTO turns (
           game_id,turn,observed_at,my_move,my_thinking_json,
@@ -69,6 +73,13 @@ class TestMergeGameplayDatabases(unittest.TestCase):
         ])
         self.assertEqual(connection.execute("SELECT COUNT(*) FROM turns").fetchone()[0], 2)
         self.assertEqual(connection.execute("SELECT COUNT(*) FROM snake_turns").fetchone()[0], 2)
+        customizations = connection.execute("""
+          SELECT game_id, customizations_json FROM game_snakes ORDER BY game_id
+        """).fetchall()
+        self.assertEqual(customizations, [
+          ("base-game", '{"color":"#663399","head":"ferret","tail":"swirl"}'),
+          ("delta-game", '{"color":"#663399","head":"ferret","tail":"swirl"}'),
+        ])
         self.assertEqual(connection.execute("PRAGMA foreign_key_check").fetchall(), [])
 
   def test_conflicting_duplicate_aborts_without_destination(self):