feat: dual pricing policies + discount VAT splitting

Add production pricing policy (id_pol_productie) for articles with cont 341/345,
smart discount VAT splitting across multiple rates, per-article id_pol support,
and mapped SKU price validation. Settings UI updated with new controls.

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

api/app/services/import_service.py

@@ -60,18 +60,81 @@ def format_address_for_oracle(address: str, city: str, region: str) -> str:
     return f"JUD:{region_clean};{city_clean};{address_clean}"
 
 
+def compute_discount_split(order, settings: dict) -> dict | None:
+    """Compute proportional discount split by VAT rate from order items.
+
+    Returns: {"11": 3.98, "21": 1.43} or None if split not applicable.
+    Only splits when split_discount_vat is enabled AND multiple VAT rates exist.
+    When single VAT rate: returns {actual_rate: total} (smarter than GoMag's fixed 21%).
+    """
+    if not order or order.discount_total <= 0:
+        return None
+
+    split_enabled = settings.get("split_discount_vat") == "1"
+
+    # Calculate VAT distribution from order items (exclude zero-value)
+    vat_totals = {}
+    for item in order.items:
+        item_value = abs(item.price * item.quantity)
+        if item_value > 0:
+            vat_key = str(int(item.vat)) if item.vat == int(item.vat) else str(item.vat)
+            vat_totals[vat_key] = vat_totals.get(vat_key, 0) + item_value
+
+    if not vat_totals:
+        return None
+
+    grand_total = sum(vat_totals.values())
+    if grand_total <= 0:
+        return None
+
+    if len(vat_totals) == 1:
+        # Single VAT rate — use that rate (smarter than GoMag's fixed 21%)
+        actual_vat = list(vat_totals.keys())[0]
+        return {actual_vat: round(order.discount_total, 2)}
+
+    if not split_enabled:
+        return None
+
+    # Multiple VAT rates — split proportionally
+    result = {}
+    discount_remaining = order.discount_total
+    sorted_rates = sorted(vat_totals.keys(), key=lambda x: float(x))
+
+    for i, vat_rate in enumerate(sorted_rates):
+        if i == len(sorted_rates) - 1:
+            split_amount = round(discount_remaining, 2)  # last gets remainder
+        else:
+            proportion = vat_totals[vat_rate] / grand_total
+            split_amount = round(order.discount_total * proportion, 2)
+            discount_remaining -= split_amount
+
+        if split_amount > 0:
+            result[vat_rate] = split_amount
+
+    return result if result else None
+
+
 def build_articles_json(items, order=None, settings=None) -> str:
     """Build JSON string for Oracle PACK_IMPORT_COMENZI.importa_comanda.
-    Includes transport and discount as extra articles if configured."""
+    Includes transport and discount as extra articles if configured.
+    Supports per-article id_pol from codmat_policy_map and discount VAT splitting."""
     articles = []
+    codmat_policy_map = settings.get("_codmat_policy_map", {}) if settings else {}
+    default_id_pol = settings.get("id_pol", "") if settings else ""
+
     for item in items:
-        articles.append({
+        article_dict = {
             "sku": item.sku,
             "quantity": str(item.quantity),
             "price": str(item.price),
             "vat": str(item.vat),
             "name": clean_web_text(item.name)
-        })
+        }
+        # Per-article id_pol from dual-policy validation
+        item_pol = codmat_policy_map.get(item.sku)
+        if item_pol and str(item_pol) != str(default_id_pol):
+            article_dict["id_pol"] = str(item_pol)
+        articles.append(article_dict)
 
     if order and settings:
         transport_codmat = settings.get("transport_codmat", "")
@@ -90,20 +153,50 @@ def build_articles_json(items, order=None, settings=None) -> str:
             if settings.get("transport_id_pol"):
                 article_dict["id_pol"] = settings["transport_id_pol"]
             articles.append(article_dict)
-        # Discount total with quantity -1 (positive price)
+
+        # Discount — smart VAT splitting
         if order.discount_total > 0 and discount_codmat:
-            # Use GoMag JSON discount VAT if available, fallback to settings
-            discount_vat = getattr(order, 'discount_vat', None) or settings.get("discount_vat", "19")
-            article_dict = {
-                "sku": discount_codmat,
-                "quantity": "-1",
-                "price": str(order.discount_total),
-                "vat": discount_vat,
-                "name": "Discount"
-            }
-            if settings.get("discount_id_pol"):
-                article_dict["id_pol"] = settings["discount_id_pol"]
-            articles.append(article_dict)
+            discount_split = compute_discount_split(order, settings)
+
+            if discount_split and len(discount_split) > 1:
+                # Multiple VAT rates — multiple discount lines
+                for vat_rate, split_amount in sorted(discount_split.items(), key=lambda x: float(x[0])):
+                    article_dict = {
+                        "sku": discount_codmat,
+                        "quantity": "-1",
+                        "price": str(split_amount),
+                        "vat": vat_rate,
+                        "name": f"Discount (TVA {vat_rate}%)"
+                    }
+                    if settings.get("discount_id_pol"):
+                        article_dict["id_pol"] = settings["discount_id_pol"]
+                    articles.append(article_dict)
+            elif discount_split and len(discount_split) == 1:
+                # Single VAT rate — use detected rate
+                actual_vat = list(discount_split.keys())[0]
+                article_dict = {
+                    "sku": discount_codmat,
+                    "quantity": "-1",
+                    "price": str(order.discount_total),
+                    "vat": actual_vat,
+                    "name": "Discount"
+                }
+                if settings.get("discount_id_pol"):
+                    article_dict["id_pol"] = settings["discount_id_pol"]
+                articles.append(article_dict)
+            else:
+                # Fallback — original behavior with GoMag VAT or settings default
+                discount_vat = getattr(order, 'discount_vat', None) or settings.get("discount_vat", "21")
+                article_dict = {
+                    "sku": discount_codmat,
+                    "quantity": "-1",
+                    "price": str(order.discount_total),
+                    "vat": discount_vat,
+                    "name": "Discount"
+                }
+                if settings.get("discount_id_pol"):
+                    article_dict["id_pol"] = settings["discount_id_pol"]
+                articles.append(article_dict)
 
     return json.dumps(articles)