Add fullscreen in-app image view, no stretch, sharing the editor's in-app/external toggle

Settings.py

@@ -155,6 +155,10 @@ def BuildSettingsDialog(
 
     UseSharedSwitch.on_change = OnUseSharedChanged
     DotfilesSwitch = ft.Switch(label="Show dotfiles", value=Config.ShowDotfiles)
+    OpenFilesInAppSwitch = ft.Switch(
+        label="Open text/config/markup files in SaraFem's own viewer, not your default app",
+        value=Config.OpenFilesInApp,
+    )
     BatchRenamePatternField = ft.TextField(
         value=Config.BatchRenamePattern,
         label="Batch rename pattern (~ = name, ! = counter, ^ = extension)",
@@ -288,6 +292,7 @@ def BuildSettingsDialog(
         "General": ft.Column(
             [
                 DotfilesSwitch,
+                OpenFilesInAppSwitch,
                 BatchRenamePatternField,
                 DeleteZipSwitch,
                 _SectionLabel("Default compress format"),
@@ -450,6 +455,7 @@ def BuildSettingsDialog(
             HideWindowTitleBar=SharedTitleBarSwitch.value,
         ).Save()
         Config.ShowDotfiles = DotfilesSwitch.value
+        Config.OpenFilesInApp = OpenFilesInAppSwitch.value
         Config.BatchRenamePattern = BatchRenamePatternField.value.strip() or "~!^"
         Config.DeleteZipAfterExtract = DeleteZipSwitch.value
         Config.DefaultArchiveFormat = GetArchiveFormat()