Add subscription pricing and Base drawing limit

tools/LmePlayVerifier/LmePlayVerifier.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Google.Apis.AndroidPublisher.v3" Version="1.76.0.4277" />
+  </ItemGroup>
+</Project>

tools/LmePlayVerifier/Program.cs

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+using Google.Apis.AndroidPublisher.v3;
+using Google.Apis.Auth.OAuth2;
+using Google.Apis.Services;
+
+const string PackageName = "it.liviomerola.lmemappecatastali.pro";
+const string ProductId = "lme_pro";
+
+var builder = WebApplication.CreateBuilder(args);
+builder.Services.AddSingleton(_ =>
+{
+    var credential = GoogleCredential.GetApplicationDefault()
+        .CreateScoped(AndroidPublisherService.Scope.Androidpublisher);
+    return new AndroidPublisherService(new BaseClientService.Initializer
+    {
+        HttpClientInitializer = credential,
+        ApplicationName = "LME Play subscription verifier"
+    });
+});
+
+var app = builder.Build();
+app.UseHttpsRedirection();
+
+app.MapGet("/health", () => Results.Ok(new { status = "ok" }));
+app.MapPost("/v1/google-play/subscriptions/verify", async (
+    VerifySubscriptionRequest request,
+    AndroidPublisherService publisher,
+    CancellationToken cancellationToken) =>
+{
+    if (request.PackageName != PackageName || request.ProductId != ProductId
+        || string.IsNullOrWhiteSpace(request.PurchaseToken))
+    {
+        return Results.BadRequest(new VerifySubscriptionResponse(false, null, "Richiesta non valida."));
+    }
+
+    try
+    {
+        var purchase = await publisher.Purchases.Subscriptionsv2
+            .Get(PackageName, request.PurchaseToken)
+            .ExecuteAsync(cancellationToken);
+        var active = purchase.SubscriptionState is "SUBSCRIPTION_STATE_ACTIVE"
+            or "SUBSCRIPTION_STATE_IN_GRACE_PERIOD";
+        var expiresAt = purchase.LineItems?
+            .Select(item => item.ExpiryTimeDateTimeOffset)
+            .Where(value => value.HasValue)
+            .Max();
+        return Results.Ok(new VerifySubscriptionResponse(
+            active,
+            expiresAt,
+            active ? "Abbonamento LME Pro verificato." : "L'abbonamento Google Play non risulta attivo."));
+    }
+    catch (Google.GoogleApiException error) when ((int)error.HttpStatusCode is 400 or 404)
+    {
+        return Results.Ok(new VerifySubscriptionResponse(false, null, "Acquisto Google Play non riconosciuto."));
+    }
+});
+
+app.Run();
+
+internal sealed record VerifySubscriptionRequest(string PackageName, string ProductId, string PurchaseToken);
+internal sealed record VerifySubscriptionResponse(bool Active, DateTimeOffset? ExpiresAt, string Message);

tools/LmePlayVerifier/README.md

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+# LME Play verifier
+
+Servizio HTTPS per verificare i token degli abbonamenti `lme_pro` con la Google Play Developer API.
+
+## Configurazione
+
+1. Creare un service account in Google Cloud e concedergli nella Play Console il permesso di visualizzare ordini e abbonamenti dell'app.
+2. Conservare il JSON del service account solo sul server.
+3. Impostare `GOOGLE_APPLICATION_CREDENTIALS` con il percorso assoluto del JSON.
+4. Pubblicare il servizio dietro HTTPS.
+5. Compilare l'app con:
+
+```powershell
+-p:PlayBillingVerificationUrl=https://example.test/v1/google-play/subscriptions/verify
+-p:PlayBillingVerificationRequired=true
+```
+
+Non inserire il JSON del service account, token di acquisto o credenziali nel repository o nell'AAB.