Refactor DbModel options to use generic entity mapping

Replaces strongly-typed view options classes with a generic EntityOptions class and a dictionary-based configuration for entity-to-view and property-to-column mappings. Updates appsettings.DbModel.json to match the new structure. Refactors RecDbContext to use extension methods for mapping configuration. Removes obsolete options classes and simplifies exception handling for missing mappings. This change improves flexibility and maintainability of database view configuration.

src/ReC.Application/Common/Exceptions/DbModelConfigurationException.cs

@@ -0,0 +1,8 @@
+namespace ReC.Application.Common.Exceptions;
+
+public class DbModelConfigurationException : Exception
+{
+    public DbModelConfigurationException() { }
+
+    public DbModelConfigurationException(string message) : base(message) { }
+}