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.

server/database/__init__.py

@@ -1,12 +1,40 @@
+from typing import TYPE_CHECKING, Any
+
 from .GameplayDatabase import GameplayDatabase
 from .backend import GameplayBackendBuilder
 
-from .LocalStorage import LocalStorage
-from .EdgeDB import EdgeDB
+if TYPE_CHECKING:
+  from .EdgeDB import EdgeDB
+  from .LocalStorage import LocalStorage
+
+__all__ = (
+  "EdgeDB",
+  "GameplayBackendBuilder",
+  "GameplayDatabase",
+  "LocalStorage",
+  "StorageLoader",
+)
+
+def __getattr__(name:str):
+  """Load optional storage backends only when explicitly requested.
+
+  Database maintenance scripts import SQLite backend modules through this
+  package. Eagerly importing LocalStorage used to make those scripts require
+  unrelated web-storage dependencies such as aiofiles.
+  """
+  if name == "LocalStorage":
+    from .LocalStorage import LocalStorage
+    return LocalStorage
+  if name == "EdgeDB":
+    from .EdgeDB import EdgeDB
+    return EdgeDB
+  raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
 
 class StorageLoader:
   @classmethod
-  def build(self, selected_storage:str) -> LocalStorage|EdgeDB:
-    storage_module = __import__(f"server.database.{selected_storage}", fromlist=[selected_storage])
+  def build(cls, selected_storage:str) -> Any:
+    storage_module = __import__(
+      f"server.database.{selected_storage}", fromlist=[selected_storage],
+    )
     storage_class = getattr(storage_module, selected_storage)
     return storage_class