fix(host): resolve Host-003,004 — replace plaintext secrets with env placeholders, validate site seed-node ports; re-triage Host-002

tests/ScadaLink.Host.Tests/CentralDbTestEnvironment.cs

@@ -0,0 +1,41 @@
+namespace ScadaLink.Host.Tests;
+
+/// <summary>
+/// Host-003: <c>appsettings.Central.json</c> no longer commits database connection
+/// strings — they are externalised to environment variables. Tests that exercise the
+/// full <c>Program</c> startup pipeline against the real SQL provider must therefore
+/// supply the local dev connection strings the way a deployment would: via
+/// environment variables (<c>Program</c>'s configuration builder calls
+/// <c>AddEnvironmentVariables()</c>).
+///
+/// Dispose restores the previous values so tests stay isolated.
+/// </summary>
+internal sealed class CentralDbTestEnvironment : IDisposable
+{
+    // Local dev/test database — same credentials the infra docker-compose stack uses.
+    // This is a test fixture value, not a committed production secret.
+    private const string ConfigurationDb =
+        "Server=localhost,1433;Database=ScadaLinkConfig;User Id=scadalink_app;Password=ScadaLink_Dev1#;TrustServerCertificate=true";
+    private const string MachineDataDb =
+        "Server=localhost,1433;Database=ScadaLinkMachineData;User Id=scadalink_app;Password=ScadaLink_Dev1#;TrustServerCertificate=true";
+
+    private const string ConfigKey = "ScadaLink__Database__ConfigurationDb";
+    private const string MachineKey = "ScadaLink__Database__MachineDataDb";
+
+    private readonly string? _previousConfig;
+    private readonly string? _previousMachine;
+
+    public CentralDbTestEnvironment()
+    {
+        _previousConfig = Environment.GetEnvironmentVariable(ConfigKey);
+        _previousMachine = Environment.GetEnvironmentVariable(MachineKey);
+        Environment.SetEnvironmentVariable(ConfigKey, ConfigurationDb);
+        Environment.SetEnvironmentVariable(MachineKey, MachineDataDb);
+    }
+
+    public void Dispose()
+    {
+        Environment.SetEnvironmentVariable(ConfigKey, _previousConfig);
+        Environment.SetEnvironmentVariable(MachineKey, _previousMachine);
+    }
+}