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>

translations/messages.en.xlf

@@ -648,6 +648,12 @@ Sub elements will be moved upwards.</target>
         <target>Export this parameter as an EDA field</target>
       </segment>
     </unit>
+    <unit id="Nx6h9XW" name="specifications.eda_symbol_visibility.help">
+      <segment state="translated">
+        <source>specifications.eda_symbol_visibility.help</source>
+        <target>Make this parameter field visible in the schematic symbol</target>
+      </segment>
+    </unit>
     <unit id="XclPxI9" name="specification.create">
       <segment state="translated">
         <source>specification.create</source>
@@ -13043,6 +13049,18 @@ Buerklin-API Authentication server:
         <target>EDA visibility for all [part] parameters who does not have an explicit visibility set. When enabled all parameters will be visible in the EDA software by default.</target>
       </segment>
     </unit>
+    <unit id="XchzDpI" name="settings.misc.kicad_eda.default_parameter_symbol_visibility">
+      <segment state="translated">
+        <source>settings.misc.kicad_eda.default_parameter_symbol_visibility</source>
+        <target>Default symbol visibility of parameters</target>
+      </segment>
+    </unit>
+    <unit id="zLHkPCx" name="settings.misc.kicad_eda.default_parameter_symbol_visibility.help">
+      <segment state="translated">
+        <source>settings.misc.kicad_eda.default_parameter_symbol_visibility.help</source>
+        <target>Whether exported [part] parameter fields that do not have an explicit symbol visibility set are shown in the schematic symbol (the KiCad field's "visible" flag). Only affects parameters that are already exported as EDA fields.</target>
+      </segment>
+    </unit>
     <unit id="J6pYnaC" name="settings.misc.kicad_eda.default_orderdetails_visibility">
       <segment state="translated">
         <source>settings.misc.kicad_eda.default_orderdetails_visibility</source>