fix(configurator): address code review findings — pricing engine + views

- Fix thickness factor: now scales linearly (thickness * factor), not
  multiplicatively. Default factor=1.0 means price scales 1:1 with mils.
- Fix batch_size: setup fee now multiplied by ceil(qty/batch_size) batches
- Fix hardcoded $ in price breakdown HTML: uses currency_id.symbol
- Add coating_config_id.certification_level to @api.depends
- Remove readonly on x_fc_receiving_status (placeholder until receiving module)
- Add currency_id to treatment list view for Monetary widget

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

fusion-plating/fusion_plating_configurator/views/fp_treatment_views.xml

@@ -16,6 +16,7 @@
                 <field name="name"/>
                 <field name="treatment_type"/>
                 <field name="default_duration_minutes"/>
+                <field name="currency_id" column_invisible="1"/>
                 <field name="default_cost"/>
                 <field name="active" widget="boolean_toggle"/>
             </list>