Add standalone wiring diagram PNG export

Fetch the wiring diagram from the VoltPlan API and share it as a
standalone PNG from the Overview share menu on both platforms, with a
localized error when the diagram cannot be generated.

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

android/app/src/main/res/values-nl/strings.xml

@@ -5,6 +5,7 @@
     <!-- Actions -->
     <string name="action_add">Toevoegen</string>
     <string name="action_back">Terug</string>
+    <string name="action_save">Opslaan</string>
     <string name="action_delete">Verwijderen</string>
 
     <!-- Systems -->
@@ -177,6 +178,8 @@
     <string name="overview_chargers_empty_subtitle">Voeg walstroom-, DC-DC- of zonneladers toe om je laadcapaciteit te begrijpen.</string>
     <string name="overview_chargers_empty_create">Lader toevoegen</string>
     <string name="overview_share_pdf">Volledig rapport (PDF)</string>
+    <string name="overview_share_diagram">Bedradingsschema</string>
+    <string name="overview_share_diagram_error">Diagram kon niet worden gegenereerd. Controleer je internetverbinding.</string>
 
     <!-- Goal editor steppers -->
     <string name="goal_days">Dagen</string>