Add DB presence check button to import phase

Lets the user spot missing components right after import instead of
discovering it later in the raw-folder step, by coloring each grid row
green/red based on a lookup against cad_index.db.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

CadSearchGui/Form1.cs

@@ -10,6 +10,7 @@ public partial class Form1 : Form
     private readonly Button _btnCreaRaw = new();
     private readonly Button _btnTrovaPrt = new();
     private readonly Button _btnReport = new();
+    private readonly Button _btnVerifica = new();
     private readonly Button _btnCompletezza = new();
     private readonly Button _btnPulisci = new();
     private readonly Label _lblStatus = new();
@@ -261,6 +262,12 @@ public partial class Form1 : Form
         btnSfoglia.Click += (_, _) => ScegliFileDistinta();
         contenuto.Controls.Add(btnSfoglia);
 
+        _btnVerifica.Text = "Verifica presenza nel DB";
+        _btnVerifica.Size = new Size(220, 32);
+        _btnVerifica.Margin = new Padding(0, 0, 0, 8);
+        _btnVerifica.Click += (_, _) => VerificaCodiciNelDb();
+        contenuto.Controls.Add(_btnVerifica);
+
         _lblImportStatus.AutoSize = false;
         _lblImportStatus.AutoEllipsis = true;
         _lblImportStatus.Height = 24;
@@ -488,6 +495,21 @@ public partial class Form1 : Form
         _tipImportStatus.SetToolTip(_lblImportStatus, testo);
     }
 
+    private void VerificaCodiciNelDb()
+    {
+        if (_righeCorrenti is null)
+            return;
+
+        var trovati = TrovaPercorsiCad(_righeCorrenti.Select(r => r.Componente));
+        foreach (DataGridViewRow riga in _gridImport.Rows)
+        {
+            string componente = (string)riga.Cells["componente"].Value!;
+            riga.DefaultCellStyle.BackColor = trovati.ContainsKey(componente)
+                ? Color.FromArgb(198, 239, 206)
+                : Color.FromArgb(255, 199, 206);
+        }
+    }
+
     private void CreaCartellaRaw()
     {
         if (_percorsoInputCorrente is null || _righeCorrenti is null)