fix(pos): enrich quotation/layaway items from inventory and allow final payment on layaway complete

Quotation and layaway endpoints were calling calculate_totals() on raw
input items without looking up unit_price/tax_rate from inventory, causing
KeyError. Added _enrich_items() helper (with customer price tier support).
Also removed non-existent discount_total column from quotations INSERT,
and made layaway complete accept a final payment for the remaining balance.

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

pos/blueprints/pos_bp.py

@@ -19,6 +19,57 @@ from services.audit import log_action
 pos_bp = Blueprint('pos', __name__, url_prefix='/pos/api')
 
 
+def _enrich_items(cur, items, customer_id=None):
+    """Look up inventory data for items that lack unit_price/tax_rate.
+
+    Returns list of dicts with all fields needed by calculate_totals.
+    """
+    enriched = []
+    for item in items:
+        inv_id = item.get('inventory_id')
+        qty = int(item.get('quantity', 1))
+        if qty <= 0:
+            raise ValueError(f"Invalid quantity for inventory_id {inv_id}")
+
+        cur.execute("""
+            SELECT id, part_number, name, cost, price_1, price_2, price_3,
+                   tax_rate, branch_id
+            FROM inventory WHERE id = %s AND is_active = true
+        """, (inv_id,))
+        inv = cur.fetchone()
+        if not inv:
+            raise ValueError(f"Inventory item {inv_id} not found or inactive")
+
+        # Determine price tier from customer if provided
+        price_tier = 1
+        if customer_id:
+            cur.execute("SELECT price_tier FROM customers WHERE id = %s", (customer_id,))
+            cust = cur.fetchone()
+            if cust and cust[0]:
+                price_tier = int(cust[0])
+
+        # price_1=inv[4], price_2=inv[5], price_3=inv[6]
+        tier_prices = {1: inv[4], 2: inv[5], 3: inv[6]}
+        default_price = float(tier_prices.get(price_tier, inv[4]) or inv[4])
+
+        unit_price = float(item.get('unit_price', default_price))
+        discount_pct = float(item.get('discount_pct', 0))
+        tax_rate = float(item.get('tax_rate', inv[7] or 0.16))
+
+        enriched.append({
+            'inventory_id': inv_id,
+            'part_number': inv[1],
+            'name': inv[2],
+            'quantity': qty,
+            'unit_price': unit_price,
+            'unit_cost': float(inv[3]) if inv[3] else 0,
+            'discount_pct': discount_pct,
+            'tax_rate': tax_rate,
+            'branch_id': inv[8],
+        })
+    return enriched
+
+
 # ─── Sales ───────────────────────────────────────
 
 @pos_bp.route('/sales', methods=['POST'])
@@ -362,8 +413,15 @@ def create_quotation():
     conn = get_tenant_conn(g.tenant_id)
     cur = conn.cursor()
 
+    # Enrich items with inventory data (price, tax, etc.)
+    try:
+        enriched = _enrich_items(cur, items, data.get('customer_id'))
+    except ValueError as e:
+        cur.close(); conn.close()
+        return jsonify({'error': str(e)}), 400
+
     # Calculate totals
-    totals = calculate_totals(items)
+    totals = calculate_totals(enriched)
 
     valid_days = int(data.get('valid_days', 7))
     valid_until = (date.today() + timedelta(days=valid_days)).isoformat()
@@ -371,24 +429,21 @@ def create_quotation():
     try:
         cur.execute("""
             INSERT INTO quotations
-                (branch_id, customer_id, employee_id, subtotal, discount_total,
+                (branch_id, customer_id, employee_id, subtotal,
                  tax_total, total, status, valid_until, notes)
-            VALUES (%s,%s,%s,%s,%s,%s,%s,'active',%s,%s)
+            VALUES (%s,%s,%s,%s,%s,%s,'active',%s,%s)
             RETURNING id, created_at
         """, (
             g.branch_id, data.get('customer_id'), g.employee_id,
-            totals['subtotal'], totals['discount_total'], totals['tax_total'],
+            totals['subtotal'], totals['tax_total'],
             totals['total'], valid_until, data.get('notes')
         ))
         quot_id, created_at = cur.fetchone()
 
         # Insert quotation items
         for item in totals['items']:
-            # Look up part_number and name from inventory
+            part_number = item.get('part_number', '')
-            cur.execute("SELECT part_number, name FROM inventory WHERE id = %s", (item['inventory_id'],))
+            name = item.get('name', '')
-            inv = cur.fetchone()
-            part_number = inv[0] if inv else item.get('part_number', '')
-            name = inv[1] if inv else item.get('name', '')
 
             line_subtotal = round(
                 item['unit_price'] * item['quantity'] * (1 - item['discount_pct'] / 100), 2
@@ -670,8 +725,15 @@ def create_layaway():
     conn = get_tenant_conn(g.tenant_id)
     cur = conn.cursor()
 
+    # Enrich items with inventory data
+    try:
+        enriched = _enrich_items(cur, items, customer_id)
+    except ValueError as e:
+        cur.close(); conn.close()
+        return jsonify({'error': str(e)}), 400
+
     # Calculate totals
-    totals = calculate_totals(items)
+    totals = calculate_totals(enriched)
 
     if initial_payment > totals['total']:
         cur.close(); conn.close()
@@ -697,11 +759,9 @@ def create_layaway():
         # Insert layaway items and reserve stock (table created by migration v1.1_pos_tables.sql)
         from services.inventory_engine import record_operation
         for item in totals['items']:
-            cur.execute("SELECT part_number, name, branch_id FROM inventory WHERE id = %s", (item['inventory_id'],))
+            part_number = item.get('part_number', '')
-            inv = cur.fetchone()
+            name = item.get('name', '')
-            part_number = inv[0] if inv else item.get('part_number', '')
+            item_branch_id = item.get('branch_id', g.branch_id)
-            name = inv[1] if inv else item.get('name', '')
-            item_branch_id = inv[2] if inv else g.branch_id
 
             line_subtotal = round(
                 item['unit_price'] * item['quantity'] * (1 - item['discount_pct'] / 100), 2
@@ -997,11 +1057,29 @@ def complete_layaway(layaway_id):
     if status != 'active':
         cur.close(); conn.close()
         return jsonify({'error': f'Layaway is {status}'}), 400
-    if paid < total:
-        cur.close(); conn.close()
-        return jsonify({'error': f'Layaway not fully paid. Remaining: ${total - paid:.2f}'}), 400
 
+    remaining = round(total - paid, 2)
     try:
+        # If there's a remaining balance, accept a final payment with the complete call
+        if remaining > 0:
+            final_method = data.get('payment_method', 'efectivo')
+            cur.execute("""
+                INSERT INTO layaway_payments
+                    (layaway_id, amount, payment_method, reference, employee_id)
+                VALUES (%s,%s,%s,%s,%s)
+            """, (layaway_id, remaining, final_method,
+                  data.get('reference', 'Pago final al completar'), g.employee_id))
+            cur.execute("UPDATE layaways SET amount_paid = total WHERE id = %s", (layaway_id,))
+            paid = total
+
+            # Record cash movement for final payment
+            register_id = data.get('register_id')
+            if register_id and final_method == 'efectivo':
+                cur.execute("""
+                    INSERT INTO cash_movements (register_id, type, amount, reason, employee_id)
+                    VALUES (%s, 'in', %s, %s, %s)
+                """, (register_id, remaining, f'Apartado #{layaway_id} - pago final', g.employee_id))
+
         # Get layaway items
         cur.execute("""
             SELECT inventory_id, quantity, unit_price, discount_pct, tax_rate