feat(fusion_clock): native recurring shifts engine [A4-A5]

fusion.clock.schedule.recurrence (repeat every N day/week/month/year;
forever/until/N-times) re-fit from planning.recurrency onto per-day rows;
daily generation cron; _fclk_on_leave skip; planner Repeat…/Stop-repeat
UI + endpoints; recurrence + role indicators on cells.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

fusion_clock/models/clock_schedule.py

@@ -377,6 +377,7 @@ class FusionClockSchedule(models.Model):
                 'role_id': schedule.role_id.id or False,
                 'role_name': schedule.role_id.name or '',
                 'role_color': schedule.role_id._get_color_from_code() if schedule.role_id else '',
+                'recurring': bool(schedule.recurrence_id),
             }
 
         plan = employee._get_fclk_day_plan(date_obj)
@@ -399,6 +400,37 @@ class FusionClockSchedule(models.Model):
             'role_color': '',
         }
 
+    @api.model
+    def fclk_attach_recurrence(self, schedule, repeat_vals):
+        """Attach a recurrence rule to a seed schedule cell and generate it
+        forward. ``repeat_vals`` mirrors the recurrence fields."""
+        schedule = schedule.sudo()
+        if not schedule:
+            raise ValidationError(_("Pick a shift to repeat first."))
+        rule = self.env['fusion.clock.schedule.recurrence'].sudo().create({
+            'repeat_interval': int(repeat_vals.get('repeat_interval') or 1),
+            'repeat_unit': repeat_vals.get('repeat_unit') or 'week',
+            'repeat_type': repeat_vals.get('repeat_type') or 'forever',
+            'repeat_until': repeat_vals.get('repeat_until') or False,
+            'repeat_number': int(repeat_vals.get('repeat_number') or 1),
+            'company_id': schedule.company_id.id or self.env.company.id,
+        })
+        schedule.recurrence_id = rule.id
+        rule._generate()
+        return rule
+
+    @api.model
+    def fclk_clear_recurrence(self, schedule):
+        """Detach + stop the recurrence on a seed cell (keeps posted rows)."""
+        schedule = schedule.sudo()
+        rule = schedule.recurrence_id
+        if rule:
+            rule._stop(fields.Date.today())
+            schedule.recurrence_id = False
+            if not rule.schedule_ids:
+                rule.unlink()
+        return True
+
     @api.model
     def fclk_email_posted_week(self, employee, week_start, week_end):
         """Email one employee a summary of their POSTED shifts for the week."""