Add explicit working folder; rename project from CadSearchGui to PrepStep

Working folder (phase 1): CSV/raw/step/step_finali all used to live split
across two different implicit locations (CSV in the "repo root" found by
walking up for CLAUDE.md, raw/step next to the input distinta file) with
neither shown to the user. That repo-root lookup also silently breaks once
the app runs as a standalone published exe on a machine with no repo/
CLAUDE.md at all. Replaced both with one explicit "cartella di lavoro",
auto-suggested (last used, remembered the same way as the DB path) and
changeable from phase 1, with no dependency on any repo marker file.

Rename: CadSearchGui was the working name from before the app had a
product identity; renamed folders, csproj files, namespace and the
AppData settings folder to PrepStep throughout, matching the exe name
already in use. Product-facing name stays "Cevolani StepPrep".

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

PrepStep/ProgressForm.cs

@@ -0,0 +1,118 @@
+namespace PrepStep;
+
+public sealed class ProgressForm : Form
+{
+    private readonly Label _lblCartella = new();
+    private readonly ProgressBar _progressBar = new();
+    private readonly Label _lblConteggio = new();
+    private readonly Label _lblDettaglio = new();
+    private readonly Label _lblEta = new();
+    private readonly Button _btnAnnulla = new();
+    private readonly ToolTip _tipCartella = new();
+
+    public event EventHandler? Annullato;
+
+    public ProgressForm()
+    {
+        Text = "Aggiornamento indice in corso...";
+        FormBorderStyle = FormBorderStyle.FixedDialog;
+        StartPosition = FormStartPosition.CenterParent;
+        MinimizeBox = false;
+        MaximizeBox = false;
+        ControlBox = false;
+        ClientSize = new Size(460, 190);
+
+        _lblCartella.Text = "Preparazione...";
+        _lblCartella.Location = new Point(16, 16);
+        // AutoSize=false + AutoEllipsis: un percorso lungo (share di rete) va troncato con "..."
+        // invece di sforare il bordo del dialog, che è FixedDialog e non si può allargare.
+        // Il testo completo resta disponibile nel tooltip (stesso pattern di Form1._lblImportStatus).
+        _lblCartella.AutoSize = false;
+        _lblCartella.AutoEllipsis = true;
+        _lblCartella.Size = new Size(428, 20);
+        _lblCartella.Font = new Font(Font, FontStyle.Bold);
+
+        _progressBar.Location = new Point(16, 44);
+        _progressBar.Size = new Size(428, 24);
+        _progressBar.Minimum = 0;
+        _progressBar.Maximum = 1000;
+        _progressBar.Style = ProgressBarStyle.Marquee;
+
+        _lblConteggio.Location = new Point(16, 80);
+        _lblConteggio.AutoSize = true;
+
+        _lblDettaglio.Location = new Point(16, 104);
+        _lblDettaglio.AutoSize = true;
+        _lblDettaglio.ForeColor = SystemColors.GrayText;
+
+        _lblEta.Location = new Point(16, 128);
+        _lblEta.AutoSize = true;
+        _lblEta.Font = new Font(Font, FontStyle.Bold);
+
+        _btnAnnulla.Text = "Annulla";
+        _btnAnnulla.Location = new Point(354, 152);
+        _btnAnnulla.Size = new Size(90, 28);
+        UiStile.Secondario(_btnAnnulla);
+        _btnAnnulla.Click += (_, e) => Annullato?.Invoke(this, e);
+
+        Controls.AddRange(new Control[]
+        {
+            _lblCartella, _progressBar, _lblConteggio, _lblDettaglio, _lblEta, _btnAnnulla
+        });
+    }
+
+    public void Aggiorna(ScanProgress p)
+    {
+        _lblCartella.Text = $"Scansione {p.Cartella}...";
+        _tipCartella.SetToolTip(_lblCartella, _lblCartella.Text);
+
+        if (p.PrevistiTotali > 0)
+        {
+            _progressBar.Style = ProgressBarStyle.Continuous;
+            double frazione = Math.Min(1.0, (double)p.FattiTotali / p.PrevistiTotali);
+            _progressBar.Value = (int)(frazione * _progressBar.Maximum);
+        }
+        else
+        {
+            _progressBar.Style = ProgressBarStyle.Marquee;
+        }
+
+        _lblConteggio.Text = p.PrevistiTotali > 0
+            ? $"{p.FattiTotali:N0} / ~{p.PrevistiTotali:N0} file"
+            : $"{p.FattiTotali:N0} file processati";
+
+        _lblDettaglio.Text = $"nuovi: {p.Nuovi:N0}   aggiornati: {p.Aggiornati:N0}   invariati: {p.Invariati:N0}"
+            + (p.Rimossi > 0 ? $"   rimossi: {p.Rimossi:N0}" : "");
+
+        _lblEta.Text = $"Trascorso: {FormatTempo(p.Trascorso)}   —   {StimaRimanente(p)}";
+    }
+
+    private static string StimaRimanente(ScanProgress p)
+    {
+        if (p.PrevistiTotali <= 0 || p.FattiTotali <= 0)
+        {
+            return "stima non disponibile";
+        }
+        double filePerSecondo = p.FattiTotali / Math.Max(p.Trascorso.TotalSeconds, 0.001);
+        if (filePerSecondo <= 0)
+        {
+            return "stima non disponibile";
+        }
+        long rimanenti = Math.Max(p.PrevistiTotali - p.FattiTotali, 0);
+        var eta = TimeSpan.FromSeconds(rimanenti / filePerSecondo);
+        return $"tempo rimanente stimato: {FormatTempo(eta)}";
+    }
+
+    private static string FormatTempo(TimeSpan t)
+    {
+        if (t.TotalHours >= 1)
+        {
+            return $"{(int)t.TotalHours}h {t.Minutes}m {t.Seconds}s";
+        }
+        if (t.TotalMinutes >= 1)
+        {
+            return $"{t.Minutes}m {t.Seconds}s";
+        }
+        return $"{t.Seconds}s";
+    }
+}