[FIX] website_sale_aplicoop: two draft-reuse and compute-field bugs

- group.order.home_delivery is a stored compute field with no inverse;
  Odoo still lets write() set it directly, so a stray direct write stuck
  instead of always being re-derived from delivery_product_id. create()
  and write() now strip it from vals, same pattern already used for slug.

- _find_recent_draft_order only bounded drafts by create_date, so a
  freshly created draft for a stale/previous pickup_date (but created
  "now") was wrongly reused. Fix requires both create_date to fall in
  the active window AND pickup_date to match when set — the latter
  alone isn't enough either, per the regression already covered by
  test_find_recent_draft_excludes_previous_cycle (observed in
  production at stage.elikabilbo.eus).

website_sale_aplicoop/controllers/website_sale_validators.py

@@ -65,21 +65,33 @@ def _get_salesperson_for_order(self, partner):
 def _find_recent_draft_order(self, partner_id, group_order, request_obj=None):
     """Return the active-cycle draft sale.order for the partner, or empty.
 
-    The active ordering period ends at group_order.cutoff_date and its length
-    depends on the order period: 7 days (weekly), 14 days (biweekly), one
-    month (monthly). One-time orders have a single cycle starting at
-    start_date (or unbounded when start_date is empty). Drafts created
-    outside this window belong to a previous cycle and must not be reused —
-    otherwise stale carts come back when the user re-enters the order page.
+    A draft only counts as "current cycle" when it satisfies BOTH of these
+    (neither is sufficient on its own — see the regression each one guards):
+
+    1) create_date falls within the active window — derived from
+       group_order.cutoff_date and the order period (7 days weekly, 14
+       biweekly, one month monthly; one-time orders use a single cycle
+       starting at start_date). Without this, a draft whose pickup_date
+       happens to match the current one only because pickup_date froze
+       across cycles (observed in production) would be wrongly reused.
+    2) When group_order.pickup_date is set, the draft's pickup_date matches
+       it exactly. Without this, a draft created "now" for a stale/previous
+       pickup_date — but still inside the current create_date window —
+       would be wrongly reused instead of starting a fresh cart.
+
+    Drafts failing either check belong to a previous cycle and must not be
+    reused — otherwise stale carts come back when the user re-enters the
+    order page.
     """
     req = request_obj or request
-    from datetime import timedelta
-
-    from dateutil.relativedelta import relativedelta
 
     if not group_order or not group_order.cutoff_date:
         return req.env["sale.order"]
 
+    from datetime import timedelta
+
+    from dateutil.relativedelta import relativedelta
+
     period_end = group_order.cutoff_date
     if group_order.period == "weekly":
         period_start = period_end - timedelta(days=6)
@@ -98,6 +110,8 @@ def _find_recent_draft_order(self, partner_id, group_order, request_obj=None):
     ]
     if period_start:
         domain.append(("create_date", ">=", f"{period_start} 00:00:00"))
+    if group_order.pickup_date:
+        domain.append(("pickup_date", "=", group_order.pickup_date))
 
     return (
         req.env["sale.order"].sudo().search(domain, order="create_date desc", limit=1)