Fix: Tilføj RETURNING id til order INSERT statements

CRITICAL BUG FIX:
- execute_insert() kalder cursor.fetchone() men INSERT havde ingen RETURNING clause
- Forårsagede '500: no results to fetch' ved order oprettelse
- Tilføjet RETURNING id til:
  * tmodule_orders INSERT (linje 222)
  * tmodule_order_lines INSERT (linje 240)
- Opdateret database.py docstring til at gøre RETURNING requirement klart

ERROR: ProgrammingError - no results to fetch
  → INSERT INTO tmodule_orders ... VALUES (...)
  → Manglede RETURNING id

app/core/database.py

@@ -85,7 +85,7 @@ def execute_query(query: str, params: tuple = None, fetch: bool = True):
 
 
 def execute_insert(query: str, params: tuple = None):
-    """Execute INSERT query and return new ID"""
+    """Execute INSERT query and return new ID (requires RETURNING id clause)"""
     conn = get_db_connection()
     try:
         with conn.cursor(cursor_factory=RealDictCursor) as cursor:

app/timetracking/backend/order_service.py

@@ -217,7 +217,8 @@ class OrderService:
                 """INSERT INTO tmodule_orders 
                    (customer_id, hub_customer_id, order_date, total_hours, hourly_rate,
                     subtotal, vat_rate, vat_amount, total_amount, status, created_by)
-                   VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, 'draft', %s)""",
+                   VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, 'draft', %s)
+                   RETURNING id""",
                 (
                     customer_id,
                     customer.get('hub_customer_id'),
@@ -241,7 +242,8 @@ class OrderService:
                     """INSERT INTO tmodule_order_lines
                        (order_id, case_id, line_number, description, quantity, unit_price,
                         line_total, time_entry_ids, case_contact, time_date, is_travel)
-                       VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s)""",
+                       VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s)
+                       RETURNING id""",
                     (
                         order_id,
                         line.case_id,