Add ECMJobRunner.Domain entities and documentation

Introduced the `ECMJobRunner.Domain` project to support both
.NET Framework 4.8 and .NET 8.0. Added `Profile`,
`ProfileSqlJob`, and `ProfileHistory` entities to map to the
database schema, including relationships and audit fields.

Updated `ECMJobRunner.Domain.csproj` to enable multi-targeting
and added dependencies for Entity Framework 6.5.1 and EF Core
8.0.11. Enabled nullable reference types and set the language
version to `latest`.

Added comprehensive documentation in `AGENTS.md` detailing the
project structure, entities, database schema, and build
instructions.

ECMJobRunner.Domain/Entities/ProfileHistory.cs

@@ -0,0 +1,80 @@
+using System;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace ECMJobRunner.Domain.Entities
+{
+    /// <summary>
+    /// Profile Execution History
+    /// Stores the execution history and results of job runner profiles
+    /// Result ID: 0 = OK; 1 = ERROR; 2 = WARNING
+    /// </summary>
+    [Table("TBJR_OUT_PROFILE_HISTORY", Schema = "dbo")]
+    public class ProfileHistory
+    {
+        /// <summary>
+        /// Primary Key
+        /// </summary>
+        [Key]
+        [Column("PK_TBJR_OUT_PROFILE_HISTORY_ID")]
+        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
+        public long Id { get; set; }
+
+        /// <summary>
+        /// Foreign Key to Profile
+        /// </summary>
+        [Required]
+        [Column("FK_TBJR_CFG_PROFILE_ID")]
+        [ForeignKey(nameof(Profile))]
+        public long ProfileId { get; set; }
+
+        /// <summary>
+        /// Result ID: 0 = OK; 1 = ERROR; 2 = WARNING
+        /// </summary>
+        [Required]
+        [Column("RESULT_ID")]
+        public byte ResultId { get; set; }
+
+        /// <summary>
+        /// Result text/message
+        /// </summary>
+        [Required]
+        [Column("RESULT_TEXT")]
+        public string ResultText { get; set; } = string.Empty;
+
+        /// <summary>
+        /// Created by
+        /// </summary>
+        [Required]
+        [Column("ADDED_WHO")]
+        [MaxLength(50)]
+        public string AddedWho { get; set; } = "DEFAULT";
+
+        /// <summary>
+        /// Created at
+        /// </summary>
+        [Required]
+        [Column("ADDED_WHEN")]
+        public DateTime AddedWhen { get; set; } = DateTime.Now;
+
+        /// <summary>
+        /// Modified by
+        /// </summary>
+        [Column("CHANGED_WHO")]
+        [MaxLength(50)]
+        public string? ChangedWho { get; set; }
+
+        /// <summary>
+        /// Modified at
+        /// </summary>
+        [Column("CHANGED_WHEN")]
+        public DateTime? ChangedWhen { get; set; }
+
+        // Navigation properties
+
+        /// <summary>
+        /// Associated Profile
+        /// </summary>
+        public virtual Profile Profile { get; set; } = null!;
+    }
+}