feat!: migrate to .NET 10 LTS (#28)

tests/InboxIntel.IntegrationTests/AuditFixesTests.cs

@@ -25,7 +25,7 @@ namespace InboxIntel.IntegrationTests;
 /// endpoints (model validation, per-user rate limits) without a real Google login.</summary>
 public class TestAuthHandler : AuthenticationHandler<AuthenticationSchemeOptions>
 {
-    public const string Scheme = "Test";
+    public new const string Scheme = "Test";
     // Stable across requests so per-user rate-limit partitions accumulate correctly.
     public static readonly string Uid = Guid.NewGuid().ToString();
 
@@ -52,6 +52,9 @@ public class AuditTestAppFactory : WebApplicationFactory<Program>
         builder.ConfigureHostConfiguration(cfg => cfg.AddInMemoryCollection(new Dictionary<string, string?>
         {
             ["Database:AutoMigrate"] = "false",
+            // Npgsql 10 eagerly validates the connection string when the DbContext is
+            // resolved (8.x was lazy); these tests never connect, but the string must parse.
+            ["ConnectionStrings:Postgres"] = "Host=localhost;Database=test;Username=test;Password=test",
             ["GoogleOAuth:ClientId"] = "test-client-id",
             ["GoogleOAuth:ClientSecret"] = "test-client-secret",
             // H-2: make the auth policy trip on the 3rd request within the window.