V2.1.0 — Formats personnalises + reperes de coupe

- Formats personnalises dans tous les menus deroulants de format :
  - "Personnalise..." : saisie libre largeur x hauteur en mm
  - "Ajouter un format..." : sauvegarder un format custom (persistant)
  - Formats custom affiches dans le dropdown avec separateur
- Reperes de coupe (Annotations > Reperes de coupe) :
  - Longueur, distance du bord, epaisseur configurables
  - Couleur : noir, gris, CMYK
  - Reperes de centrage optionnels
  - Appliquer a : toutes, paires, impaires, page courante
  - Enlever les reperes de coupe (menu)
- Step & Repeat : ajout des marges (haut, bas, gauche, droite)
- Tous les dialogues de format migres vers format_combo

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/engine/crop_marks.py

@@ -0,0 +1,85 @@
+"""Moteur Reperes de coupe autonomes."""
+
+from pypdf import PdfReader, PdfWriter
+from reportlab.pdfgen import canvas
+from .pdf_utils import get_page_size
+import io
+
+
+def add_crop_marks(input_path, output_path, mark_length=14.17, mark_offset=7.09,
+                   line_width=0.25, color=(0, 0, 0), center_marks=False,
+                   apply_to="all", current_page=0):
+    """Ajouter des reperes de coupe sur les pages."""
+    reader = PdfReader(input_path)
+    writer = PdfWriter()
+
+    for i, page in enumerate(reader.pages):
+        page_num = i + 1
+        should_apply = False
+        if apply_to == "all":
+            should_apply = True
+        elif apply_to == "even":
+            should_apply = page_num % 2 == 0
+        elif apply_to == "odd":
+            should_apply = page_num % 2 != 0
+        elif apply_to == "current":
+            should_apply = i == current_page
+
+        if should_apply:
+            w, h = get_page_size(page)
+            packet = io.BytesIO()
+            c = canvas.Canvas(packet, pagesize=(w, h))
+            c.setLineWidth(line_width)
+            c.setStrokeColorRGB(*color)
+
+            # 4 coins
+            corners = [(0, 0), (w, 0), (0, h), (w, h)]
+            for cx, cy in corners:
+                # Traits horizontaux
+                if cx == 0:
+                    c.line(cx - mark_offset - mark_length, cy, cx - mark_offset, cy)
+                else:
+                    c.line(cx + mark_offset, cy, cx + mark_offset + mark_length, cy)
+                # Traits verticaux
+                if cy == 0:
+                    c.line(cx, cy - mark_offset - mark_length, cx, cy - mark_offset)
+                else:
+                    c.line(cx, cy + mark_offset, cx, cy + mark_offset + mark_length)
+
+            # Reperes de centrage
+            if center_marks:
+                mid_x = w / 2
+                mid_y = h / 2
+                ml = mark_length * 0.7
+                # Haut
+                c.line(mid_x, h + mark_offset, mid_x, h + mark_offset + ml)
+                # Bas
+                c.line(mid_x, -mark_offset, mid_x, -mark_offset - ml)
+                # Gauche
+                c.line(-mark_offset, mid_y, -mark_offset - ml, mid_y)
+                # Droite
+                c.line(w + mark_offset, mid_y, w + mark_offset + ml, mid_y)
+
+            c.showPage()
+            c.save()
+            packet.seek(0)
+            overlay = PdfReader(packet)
+            page.merge_page(overlay.pages[0])
+
+        writer.add_page(page)
+
+    with open(output_path, "wb") as f:
+        writer.write(f)
+    return output_path
+
+
+def remove_crop_marks(input_path, output_path):
+    """Enlever les reperes de coupe (remet mediabox = cropbox)."""
+    reader = PdfReader(input_path)
+    writer = PdfWriter()
+    for page in reader.pages:
+        page.cropbox = page.mediabox
+        writer.add_page(page)
+    with open(output_path, "wb") as f:
+        writer.write(f)
+    return output_path