feat: add BendLineDialog for manual bend line property entry

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

OpenNest/Forms/BendLineDialog.cs

@@ -0,0 +1,103 @@
+using OpenNest.Bending;
+using System;
+using System.Drawing;
+using System.Windows.Forms;
+
+namespace OpenNest.Forms
+{
+    public class BendLineDialog : Form
+    {
+        private readonly ComboBox cboDirection;
+        private readonly NumericUpDown numAngle;
+        private readonly NumericUpDown numRadius;
+        private readonly CheckBox chkRadius;
+
+        public BendLineDialog()
+        {
+            Text = "Bend Line Properties";
+            FormBorderStyle = FormBorderStyle.FixedDialog;
+            MaximizeBox = false;
+            MinimizeBox = false;
+            StartPosition = FormStartPosition.CenterParent;
+            Size = new Size(260, 200);
+
+            var font = new Font("Segoe UI", 9f);
+
+            // Direction
+            var lblDir = new Label { Text = "Direction:", Location = new Point(12, 15), AutoSize = true, Font = font };
+            cboDirection = new ComboBox
+            {
+                DropDownStyle = ComboBoxStyle.DropDownList,
+                Location = new Point(100, 12),
+                Width = 130,
+                Font = font
+            };
+            cboDirection.Items.AddRange(new object[] { "Down", "Up" });
+            cboDirection.SelectedIndex = 0;
+
+            // Angle
+            var lblAngle = new Label { Text = "Angle:", Location = new Point(12, 47), AutoSize = true, Font = font };
+            numAngle = new NumericUpDown
+            {
+                Location = new Point(100, 44),
+                Width = 130,
+                Font = font,
+                Minimum = 0,
+                Maximum = 180,
+                DecimalPlaces = 1,
+                Value = 90
+            };
+
+            // Radius (with checkbox to enable)
+            chkRadius = new CheckBox { Text = "Radius:", Location = new Point(12, 79), AutoSize = true, Font = font };
+            numRadius = new NumericUpDown
+            {
+                Location = new Point(100, 76),
+                Width = 130,
+                Font = font,
+                Minimum = 0,
+                Maximum = 25,
+                DecimalPlaces = 3,
+                Increment = 0.0625m,
+                Enabled = false
+            };
+            chkRadius.CheckedChanged += (s, e) => numRadius.Enabled = chkRadius.Checked;
+
+            // Buttons
+            var btnOk = new Button
+            {
+                Text = "OK",
+                DialogResult = DialogResult.OK,
+                Location = new Point(62, 120),
+                Size = new Size(80, 28),
+                Font = font
+            };
+            var btnCancel = new Button
+            {
+                Text = "Cancel",
+                DialogResult = DialogResult.Cancel,
+                Location = new Point(150, 120),
+                Size = new Size(80, 28),
+                Font = font
+            };
+
+            AcceptButton = btnOk;
+            CancelButton = btnCancel;
+
+            Controls.AddRange(new Control[] {
+                lblDir, cboDirection,
+                lblAngle, numAngle,
+                chkRadius, numRadius,
+                btnOk, btnCancel
+            });
+        }
+
+        public BendDirection Direction => cboDirection.SelectedIndex == 0
+            ? BendDirection.Down
+            : BendDirection.Up;
+
+        public double BendAngle => (double)numAngle.Value;
+
+        public double? BendRadius => chkRadius.Checked ? (double)numRadius.Value : null;
+    }
+}