fix(database): qualify RD21 saves against pinned MariaDB 12.2.2

JobTrackerApi/Data/DatabaseConfiguration.cs

@@ -0,0 +1,39 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace JobTrackerApi.Data;
+
+public static class DatabaseConfiguration
+{
+    public static string GetProvider(IConfiguration configuration) =>
+        (configuration["Database:Provider"] ?? "mariadb").Trim().ToLowerInvariant() switch
+        {
+            "mysql" or "mariadb" => "mariadb",
+            "sqlite" => "sqlite",
+            _ => throw new InvalidOperationException("Database:Provider must be mariadb (or mysql) or explicitly sqlite for transitional preservation."),
+        };
+
+    public static string GetConnectionString(IConfiguration configuration, string sqlitePath)
+    {
+        var provider = GetProvider(configuration);
+        var connection = configuration.GetConnectionString("JobTracker");
+        if (!string.IsNullOrWhiteSpace(connection)) return connection;
+        if (provider == "sqlite") return $"Data Source={sqlitePath}";
+        throw new InvalidOperationException("ConnectionStrings:JobTracker is required for MariaDB. SQLite is only used when Database:Provider is explicitly sqlite.");
+    }
+
+    public static void Configure(DbContextOptionsBuilder options, IConfiguration configuration, string sqlitePath)
+    {
+        var provider = GetProvider(configuration);
+        var connection = GetConnectionString(configuration, sqlitePath);
+        if (provider == "mariadb")
+        {
+            var configuredVersion = configuration["Database:ServerVersion"] ?? "12.2.2";
+            if (!Version.TryParse(configuredVersion, out var version) || version.Major < 1 || version.Build < 0)
+                throw new InvalidOperationException("Database:ServerVersion must be a MariaDB version in major.minor.patch form.");
+            // AutoDetect would open a server connection while options are being registered.
+            options.UseMySql(connection, new MariaDbServerVersion(version), mysql => mysql.MigrationsAssembly("JobTrackerApi"));
+        }
+        else
+            options.UseSqlite(connection, sqlite => sqlite.MigrationsAssembly("JobTrackerApi"));
+    }
+}