feat(fusion_planning): auto-publish new shifts + bulk-assign to many employees

Two manager-side time savers on the Add Shift dialog:

1. Auto-publish on create
   Override planning.slot.create() to default state='published' for
   every new shift (was: 'draft', requiring a separate Publish step
   per slot — painful with recurrence which can generate dozens at
   a time). Recurrency-generated copies inherit the parent slot's
   state, so a single recurring shift now publishes the whole series
   in one save. Manager can still pass state='draft' explicitly to
   opt out.

2. Apply Also To (multi-resource bulk create)
   New x_fc_additional_resource_ids m2m on planning.slot. When set,
   create() splits the vals into one slot per additional resource
   (deduped against the primary). Combined with recurrence, picking
   N employees and a date range now creates the full N x M shift
   matrix in a single Save instead of N manual repeats.

   Field appears in the Add Shift dialog under Role, hidden once
   the slot is saved (it's a create-time helper, not ongoing data),
   and gated to planning.group_planning_manager.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_planning/__init__.py

@@ -1,2 +1,3 @@
 # -*- coding: utf-8 -*-
 from . import controllers
+from . import models