fix(sub12a): rename _seed_default_inputs → action_seed_default_inputs

Odoo 19 rejects view buttons that call private (underscore-prefixed)
methods. Renamed the public entry point. The post_init_hook callers
follow.

Caught by entech upgrade (ParseError on the form view).

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

fusion_plating/fusion_plating/__init__.py

@@ -155,7 +155,7 @@ def _create_template_from_node(env, node, seen):
 
     tpl = env['fp.step.template'].create(vals)
     if kind:
-        tpl._seed_default_inputs()
+        tpl.action_seed_default_inputs()
 
 
 def _seed_minimal_library(env):
@@ -180,7 +180,7 @@ def _seed_minimal_library(env):
     ]
     for name, kind in minimal:
         tpl = Tpl.create({'name': name, 'default_kind': kind})
-        tpl._seed_default_inputs()
+        tpl.action_seed_default_inputs()
     _logger.info(
         'Fusion Plating: seeded minimal step library (%s entries)',
         len(minimal),