feat: add BomImportForm file browsing and analysis logic

Task 8: BrowseBom_Click auto-fills DXF folder and derives job name by
stripping ' BOM' suffix; BrowseDxf_Click opens folder browser;
Analyze_Click reads BOM via BomReader, runs BomAnalyzer, populates
DataGridView with material/thickness/parts/qty columns, updates summary
label with skipped/unmatched counts, and enables Create Nests button.

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

OpenNest/Forms/BomImportForm.cs

@@ -25,14 +25,103 @@ namespace OpenNest.Forms
 
         private void BrowseBom_Click(object sender, EventArgs e)
         {
+            using var dlg = new OpenFileDialog
+            {
+                Title = "Select BOM File",
+                Filter = "Excel Files|*.xlsx|All Files|*.*",
+                FilterIndex = 1,
+            };
+
+            if (dlg.ShowDialog(this) != DialogResult.OK)
+                return;
+
+            txtBomFile.Text = dlg.FileName;
+
+            // Default DXF folder to the same directory as the BOM file
+            if (string.IsNullOrWhiteSpace(txtDxfFolder.Text))
+                txtDxfFolder.Text = Path.GetDirectoryName(dlg.FileName);
+
+            // Derive job name by stripping " BOM" suffix and extension
+            if (string.IsNullOrWhiteSpace(txtJobName.Text))
+            {
+                var name = Path.GetFileNameWithoutExtension(dlg.FileName);
+                if (name.EndsWith(" BOM", StringComparison.OrdinalIgnoreCase))
+                    name = name.Substring(0, name.Length - 4).TrimEnd();
+                txtJobName.Text = name;
+            }
         }
 
         private void BrowseDxf_Click(object sender, EventArgs e)
         {
+            using var dlg = new FolderBrowserDialog
+            {
+                Description = "Select DXF Folder",
+                SelectedPath = txtDxfFolder.Text,
+            };
+
+            if (dlg.ShowDialog(this) != DialogResult.OK)
+                return;
+
+            txtDxfFolder.Text = dlg.SelectedPath;
         }
 
         private void Analyze_Click(object sender, EventArgs e)
         {
+            if (!File.Exists(txtBomFile.Text))
+            {
+                MessageBox.Show("BOM file does not exist.", "Validation Error",
+                    MessageBoxButtons.OK, MessageBoxIcon.Warning);
+                return;
+            }
+
+            try
+            {
+                List<BomItem> items;
+                using (var reader = new BomReader(txtBomFile.Text))
+                    items = reader.GetItems();
+
+                _analysis = BomAnalyzer.Analyze(items, txtDxfFolder.Text);
+
+                PopulateGrid(_analysis);
+                UpdateSummary(_analysis);
+                btnCreateNests.Enabled = _analysis.Groups.Count > 0;
+            }
+            catch (Exception ex)
+            {
+                MessageBox.Show($"Error reading BOM: {ex.Message}", "Error",
+                    MessageBoxButtons.OK, MessageBoxIcon.Error);
+            }
+        }
+
+        private void PopulateGrid(BomAnalysis analysis)
+        {
+            var table = new DataTable();
+            table.Columns.Add("Material", typeof(string));
+            table.Columns.Add("Thickness", typeof(string));
+            table.Columns.Add("Parts", typeof(int));
+            table.Columns.Add("Total Qty", typeof(int));
+
+            foreach (var group in analysis.Groups)
+            {
+                var partCount = group.Parts.Count;
+                var totalQty = group.Parts.Sum(p => p.Item.Qty ?? 0);
+                table.Rows.Add(group.Material, group.Thickness.ToString("0.###"), partCount, totalQty);
+            }
+
+            dgvGroups.DataSource = table;
+        }
+
+        private void UpdateSummary(BomAnalysis analysis)
+        {
+            var parts = new List<string>();
+            if (analysis.Skipped.Count > 0)
+                parts.Add($"{analysis.Skipped.Count} skipped");
+            if (analysis.Unmatched.Count > 0)
+                parts.Add($"{analysis.Unmatched.Count} unmatched");
+
+            lblSummary.Text = parts.Count > 0
+                ? string.Join(", ", parts)
+                : string.Empty;
         }
 
         private void CreateNests_Click(object sender, EventArgs e)