Document SQLite persistence and local reset behavior

README.md

@@ -7,6 +7,13 @@ Fresh full-stack starter scaffold:
 - `RpgRoller.Tests/`: xUnit integration-heavy test project
 - `RpgRoller.sln`: solution used by local CI script
 
+Backend state persistence:
+
+- EF Core with SQLite (`Microsoft.EntityFrameworkCore.Sqlite`)
+- Development DB: `RpgRoller/App_Data/rpgroller.development.db`
+- Default DB: `RpgRoller/App_Data/rpgroller.db`
+- Database schema is created automatically on startup (`EnsureCreated`)
+
 ## Prerequisites
 
 - .NET SDK 10.0+
@@ -25,6 +32,8 @@ Fresh full-stack starter scaffold:
    ```
 3. Open `http://localhost:5000` (or the port shown in the console).
 
+To use a custom SQLite database path, set `ConnectionStrings__RpgRoller`.
+
 ## Frontend Tooling
 
 - OpenAPI contract: `openapi/RpgRoller.json`