Refactor entities: remove preprocessor directives, unify style

Large-scale cleanup of entity and interface classes:
- Removed obsolete #if NET/NETFRAMEWORK preprocessor blocks
- Unified class/property formatting and indentation
- Standardized use of data annotations
- Improved nullable reference type handling
- Simplified interfaces (IHasEnvelope, IHasReceiver)
- Removed redundant and dead code
- No changes to business logic or data model

These changes modernize and standardize the codebase for easier maintenance and .NET compatibility.

EnvelopeGenerator.Domain/Entities/ElementAnnotation.cs

@@ -6,88 +6,80 @@ using System.ComponentModel.DataAnnotations.Schema;
 #endif
 
 namespace EnvelopeGenerator.Domain.Entities
-#if NET
-    ;
-#elif NETFRAMEWORK
 {
-#endif
+    [Table("TBSIG_DOCUMENT_RECEIVER_ELEMENT_ANNOTATION")]
+    public class ElementAnnotation : IHasAddedWhen, IHasChangedWhen, IHasChangedWho
+    {
+        [Key]
+        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
+        [Column("GUID", TypeName = "bigint")]
+        public long Id { get; set; }
 
-[Table("TBSIG_DOCUMENT_RECEIVER_ELEMENT_ANNOTATION")]
-public class ElementAnnotation : IHasAddedWhen, IHasChangedWhen, IHasChangedWho
-{
-    [Key]
-    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
-    [Column("GUID", TypeName = "bigint")]
-    public long Id { get; set; }
+        [Required]
+        [Column("ELEMENT_ID", TypeName = "int")]
+        public int ElementId { get; set; }
 
-    [Required]
-    [Column("ELEMENT_ID", TypeName = "int")]
-    public int ElementId { get; set; }
+        [Required]
+        [Column("NAME", TypeName = "nvarchar(100)")]
+        [StringLength(100)]
+        public string Name { get; set; }
 
-    [Required]
-    [Column("NAME", TypeName = "nvarchar(100)")]
-    [StringLength(100)]
-    public string Name { get; set; }
+        [Required]
+        [Column("VALUE", TypeName = "nvarchar(max)")]
+        public string Value { get; set; }
 
-    [Required]
-    [Column("VALUE", TypeName = "nvarchar(max)")]
-    public string Value { get; set; }
+        [Required]
+        [Column("TYPE", TypeName = "nvarchar(50)")]
+        public string Type { get; set; }
 
-    [Required]
-    [Column("TYPE", TypeName = "nvarchar(50)")]
-    public string Type { get; set; }
-
-    [Column("POSITION_X", TypeName = "float")]
-    public double
-#if NET
-        ?
-#endif
-        X { get; set; }
-
-    [Column("POSITION_Y", TypeName = "float")]
-    public double
-#if NET
-        ?
-#endif
-        Y { get; set; }
-
-    [Column("WIDTH", TypeName = "float")]
-    public double
-#if NET
-        ?
-#endif
-        Width { get; set; }
-
-    [Column("HEIGHT", TypeName = "float")]
-    public double
-#if NET
-        ?
-#endif
-        Height { get; set; }
-
-    [Required]
-    [Column("ADDED_WHEN", TypeName = "datetime")]
-    public DateTime AddedWhen { get; set; }
-
-    [Column("CHANGED_WHEN", TypeName = "datetime")]
-    public DateTime? ChangedWhen { get; set; }
-
-    [Column("CHANGED_WHO", TypeName = "nvarchar(100)")]
-    [StringLength(100)]
-    public string
+        [Column("POSITION_X", TypeName = "float")]
+        public double
 #if nullable
-        ?
+            ?
 #endif
-        ChangedWho { get; set; }
+            X { get; set; }
 
-    [ForeignKey("ElementId")]
-    public virtual Signature
+        [Column("POSITION_Y", TypeName = "float")]
+        public double
 #if nullable
-        ?
+            ?
 #endif
-        Element { get; set; }
-}
+            Y { get; set; }
 
-#if NETFRAMEWORK
+        [Column("WIDTH", TypeName = "float")]
+        public double
+#if nullable
+            ?
+#endif
+            Width { get; set; }
+
+        [Column("HEIGHT", TypeName = "float")]
+        public double
+#if nullable
+            ?
+#endif
+            Height { get; set; }
+
+        [Required]
+        [Column("ADDED_WHEN", TypeName = "datetime")]
+        public DateTime AddedWhen { get; set; }
+
+        [Column("CHANGED_WHEN", TypeName = "datetime")]
+        public DateTime? ChangedWhen { get; set; }
+
+        [Column("CHANGED_WHO", TypeName = "nvarchar(100)")]
+        [StringLength(100)]
+        public string
+#if nullable
+            ?
+#endif
+            ChangedWho { get; set; }
+
+        [ForeignKey("ElementId")]
+        public virtual Signature
+#if nullable
+            ?
+#endif
+            Element { get; set; }
     }
-#endif
+}