Refactor repository pattern and modernize codebase

Removed `SaveChangesAsync` from `IRepository` and `Repository` to centralize transaction management in `DbContext`. Updated `CfgProfileRepository` to use `Context` property instead of `_context`. Refactored `Repository` class to use C# 9.0 record-like constructor syntax and replaced private fields with properties (`Context`, `DbSet`, `Mapper`).

Replaced `Any()` with `Count == 0` for null checks and updated `FindAsync` to use C# 11 object array syntax. Added conditional compilation for framework-specific differences. These changes improve readability, consistency, and leverage modern C# features.

ECMJobRunner.Infrastructure/Repositories/CfgProfileRepository.cs

@@ -31,7 +31,7 @@ namespace ECMJobRunner.Infrastructure.Repositories
         /// </summary>
         public async Task<CfgProfile?> GetByIdWithSqlJobsAsync(long id, CancellationToken cancellationToken = default)
         {
-            return await _context.CfgProfiles
+            return await Context.CfgProfiles
                 .Include(p => p.SqlJobs)
                 .FirstOrDefaultAsync(p => p.Id == id, cancellationToken);
         }
@@ -41,7 +41,7 @@ namespace ECMJobRunner.Infrastructure.Repositories
         /// </summary>
         public async Task<List<CfgProfile>> GetAllActiveWithSqlJobsAsync(CancellationToken cancellationToken = default)
         {
-            return await _context.CfgProfiles
+            return await Context.CfgProfiles
                 .Include(p => p.SqlJobs)
                 .Where(p => p.Active)
                 .ToListAsync(cancellationToken);