refactor: address code review findings across all projects

Apply comprehensive fixes from code reviews including:
- Extract shared utilities (SqlFormatHelper, CellValueConverter, DbDestinationBase)
- Add interface abstractions (IAuthenticationService, IDatabaseMigrator, IMisQueryBuilder)
- Implement SecureStore for encrypted secrets storage
- Fix error handling with proper HTTP status codes and logging
- Optimize double enumeration in DevEtlRegistry
- Add DataSync.Dev README for developer onboarding
- Extract filter panel base classes to reduce duplication
- Update code review docs to mark all issues as fixed

NEW/tests/JdeScoping.Api.Tests/Controllers/FileControllerTests.cs

@@ -77,15 +77,15 @@ public class FileControllerTests
     }
 
     [Fact]
-    public async Task UploadWorkOrders_NoFile_ReturnsError()
+    public async Task UploadWorkOrders_NoFile_ReturnsBadRequest()
     {
         // Act
         var result = await _controller.UploadWorkOrders(null, CancellationToken.None);
 
-        // Assert
-        result.Result.ShouldBeOfType<OkObjectResult>();
-        var okResult = (OkObjectResult)result.Result!;
-        var uploadResult = okResult.Value.ShouldBeOfType<FileUploadResult<WorkOrderViewModel>>();
+        // Assert - should return BadRequest for validation errors, not 200 OK
+        result.Result.ShouldBeOfType<BadRequestObjectResult>();
+        var badRequestResult = (BadRequestObjectResult)result.Result!;
+        var uploadResult = badRequestResult.Value.ShouldBeOfType<FileUploadResult<WorkOrderViewModel>>();
         uploadResult.WasSuccessful.ShouldBeFalse();
         uploadResult.ErrorMessage.ShouldBe("No file uploaded");
     }