feat(fusion_clock): schedule parity — overnight, split shifts, open shifts [B1-B3]

is_open + crosses_midnight fields; employee_id optional (open shifts);
company_id computed w/ env.company fallback; drop hard one-per-day UNIQUE
(allow split + open). Overnight math in planned_hours/_check_schedule_times/
scheduled_times. _get_fclk_day_plan resolves multiple posted rows into ONE
work-window so penalties/overtime/absence stay correct. Migration drops the
old constraint defensively. Tests for overnight, window, open shifts.

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

fusion_clock/migrations/19.0.5.0.0/post-migrate.py

@@ -24,6 +24,14 @@ def migrate(cr, version):
     lives in fusion.clock.schedule._fclk_port_planning_data so it can be unit
     tested on an Enterprise clone where planning is installed."""
     env = api.Environment(cr, SUPERUSER_ID, {})
+
+    # Phase B drops the hard one-shift-per-day uniqueness so split/open shifts
+    # are allowed. Odoo drops removed declarative constraints on upgrade, but be
+    # explicit so the upgrade can never leave the old constraint behind.
+    cr.execute(
+        "ALTER TABLE fusion_clock_schedule "
+        "DROP CONSTRAINT IF EXISTS fusion_clock_schedule_employee_date_unique")
+
     ICP = env['ir.config_parameter'].sudo()
     if ICP.get_param(_MARKER):
         _logger.info("Fusion Clock: planning data already migrated; skipping.")