Implement per-school save functionality by introducing a dedicated save directory and updating the school management system to support loading and saving school states. Revise documentation to reflect these changes, including updates to the architecture and design documents, and enhance the API for reloading schools from disk. Update tests to ensure proper functionality of the new save and reload features.

.gitignore

@@ -418,3 +418,6 @@ FodyWeavers.xsd
 # h-school
 src/HSchool.Client/dist/
 *.tsbuildinfo
+
+# Per-school save files written next to the server when running locally
+**/saves/