Add per-parameter "visible in symbol" flag for KiCad EDA export (#1444)

* Add per-parameter "visible in symbol" flag for KiCad EDA export

Introduce a nullable tri-state eda_symbol_visibility on part parameters
that drives the KiCad field's "visible" flag in the EDA HTTP-library API
response. This is independent of the existing eda_visibility, which only
controls whether the parameter is exported as a field at all.

When the per-parameter flag is null, the new system default
KiCadEDASettings::defaultParameterSymbolVisibility applies. Both default
such that exported parameter fields keep their previous behavior
("visible": "False"), so the change is backward compatible.

- Entity: eda_symbol_visibility column + accessors, with matching
  serialization groups and a multi-platform migration
- Form: second TriStateCheckboxType, shown for part parameters only
- KiCadHelper: resolve the flag (explicit, else system default) and pass
  it to createField()
- Settings: defaultParameterSymbolVisibility (default false)
- Templates: new eye-icon column in the specifications table
- Translations (en) + tests

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

* Fixed message ids

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Jan Böhmer <mail@jan-boehmer.de>

src/Form/ParameterType.php

@@ -156,6 +156,11 @@ class ParameterType extends AbstractType
                 'label' => false,
                 'required' => false,
             ]);
+
+            $builder->add('eda_symbol_visibility', TriStateCheckboxType::class, [
+                'label' => false,
+                'required' => false,
+            ]);
         }
     }