feat: improve patient flow and pricing workflow

lib/core/services/pricing_service.dart

@@ -0,0 +1,87 @@
+import '../../models/clinic_discount.dart';
+import '../../models/job.dart';
+import '../../models/prosthetic_product.dart';
+
+class PricingBreakdown {
+  const PricingBreakdown({
+    required this.billableUnits,
+    required this.unitPrice,
+    required this.baseAmount,
+    required this.discountAmount,
+    required this.finalAmount,
+    required this.appliedDiscounts,
+  });
+
+  final int billableUnits;
+  final double unitPrice;
+  final double baseAmount;
+  final double discountAmount;
+  final double finalAmount;
+  final List<ClinicDiscount> appliedDiscounts;
+}
+
+class PricingService {
+  PricingService._();
+  static final instance = PricingService._();
+
+  int billableUnitsForType(ProstheticType type, int memberCount) {
+    final safeCount = memberCount <= 0 ? 1 : memberCount;
+    return switch (type) {
+      ProstheticType.tamProtez || ProstheticType.parsiyel => 1,
+      _ => safeCount,
+    };
+  }
+
+  String unitLabelForType(ProstheticType type) {
+    return switch (type) {
+      ProstheticType.tamProtez || ProstheticType.parsiyel => 'vaka',
+      _ => 'diş',
+    };
+  }
+
+  PricingBreakdown calculate({
+    required ProstheticProduct product,
+    required ProstheticType prostheticType,
+    required int memberCount,
+    required String clinicTenantId,
+    required List<ClinicDiscount> discounts,
+  }) {
+    final billableUnits = billableUnitsForType(prostheticType, memberCount);
+    final unitPrice = product.unitPrice ?? 0;
+    final baseAmount = unitPrice * billableUnits;
+
+    final applicable = discounts.where((discount) {
+      if (!discount.isActive) return false;
+      if (!(discount.appliesToAll || discount.clinicTenantId == clinicTenantId)) {
+        return false;
+      }
+      if (!(discount.appliesToAllTypes ||
+          discount.prostheticType == prostheticType.value)) {
+        return false;
+      }
+      if (discount.minQuantity > 0 && billableUnits < discount.minQuantity) {
+        return false;
+      }
+      return true;
+    }).toList();
+
+    double running = baseAmount;
+    for (final discount in applicable) {
+      running = discount.discountType == DiscountType.percentage
+          ? running * (1 - discount.discountValue / 100)
+          : running - discount.discountValue;
+    }
+
+    final finalAmount = running.clamp(0, double.infinity).toDouble();
+    return PricingBreakdown(
+      billableUnits: billableUnits,
+      unitPrice: unitPrice,
+      baseAmount: baseAmount,
+      discountAmount: (baseAmount - finalAmount)
+          .clamp(0, double.infinity)
+          .toDouble(),
+      finalAmount: finalAmount,
+      appliedDiscounts: applicable,
+    );
+  }
+}