Add wizard UI, general-assembly resolution, and test suite

Restructure Form1 into a sequential wizard (database -> import -> raw ->
recursive component resolution -> completeness/STEP report), fix
case-sensitivity bugs in codice/tipo_file lookups and a word-boundary gap
in the assembly scanner that missed _D100-style sub-assembly references,
and treat the distinta's general assembly as an ordinary CSV row (derived
from the DBP_<codice>_<timestamp> filename) instead of special-casing it
throughout. Also adds CadSearchGui.Tests (xUnit) covering the scanner,
filename parsing, and the case-insensitive DB lookup behavior.

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

CadSearchGui/DistintaBaseImporter.cs

@@ -14,6 +14,12 @@ static class DistintaBaseImporter
     private static readonly XNamespace Ss = "urn:schemas-microsoft-com:office:spreadsheet";
     private const string NomeFoglio = "Distinta Base";
 
+    // Il gestionale esporta la distinta come "DBP_<codice assieme generale>_<timestamp>.xls":
+    // il foglio elenca solo i componenti SOTTO l'assieme, non l'assieme generale in sé, quindi
+    // va aggiunto a parte al CSV leggendo questo codice dal nome del file di input.
+    private static readonly System.Text.RegularExpressions.Regex NomeFileDistintaRegex =
+        new(@"^DBP_(?<codice>\d+)_\d+$", System.Text.RegularExpressions.RegexOptions.Compiled);
+
     static DistintaBaseImporter()
     {
         Encoding.RegisterProvider(System.Text.CodePagesEncodingProvider.Instance);
@@ -29,6 +35,14 @@ static class DistintaBaseImporter
             .Where(r => r.Componente.Length > 0 || r.Descrizione.Length > 0)
             .ToList();
 
+        var matchGenerale = NomeFileDistintaRegex.Match(Path.GetFileNameWithoutExtension(percorsoInput));
+        if (matchGenerale.Success)
+        {
+            string codiceGenerale = matchGenerale.Groups["codice"].Value;
+            if (!righe.Any(r => string.Equals(r.Componente, codiceGenerale, StringComparison.OrdinalIgnoreCase)))
+                righe.Insert(0, (codiceGenerale, "Assieme generale"));
+        }
+
         var percorsoCsv = Path.Combine(
             Path.GetDirectoryName(Path.GetFullPath(percorsoInput))!,
             Path.GetFileNameWithoutExtension(percorsoInput) + ".csv");