Refactor API/service boundaries and modularize frontend

README.md

@@ -7,6 +7,22 @@ Fresh full-stack starter scaffold:
 - `RpgRoller.Tests/`: xUnit integration-heavy test project
 - `RpgRoller.sln`: solution used by local CI script
 
+## Code Organization
+
+Backend:
+
+- `RpgRoller/Program.cs`: thin app bootstrap only
+- `RpgRoller/Hosting/`: service registration + startup initialization
+- `RpgRoller/Api/`: endpoint mapping modules, API-to-service request mapping, auth/session filter helpers
+- `RpgRoller/Services/`: game workflows and service-layer command models (`*Command` records)
+
+Frontend:
+
+- `RpgRoller/frontend/app.ts`: orchestration entrypoint
+- `RpgRoller/frontend/app/`: split modules (`dom`, `state`, `loaders`, `render`, `events`, `actions`)
+- `RpgRoller/frontend/generated/`: generated API client source
+- `RpgRoller/wwwroot/`: compiled browser assets
+
 Backend state persistence:
 
 - EF Core with SQLite (`Microsoft.EntityFrameworkCore.Sqlite`)