fix(web): hide unsupported plugin manager

Fixes #567

src/app/view/mod.rs

@@ -2299,12 +2299,12 @@ pub(super) fn start_page_view<'a>(
         )
         .into(),
         outline_btn("Options", Message::OptionsOpen).into(),
-        outline_btn("Plugins", Message::PluginManagerOpen).into(),
     ];
-    // The web build is already in the browser, so only the desktop offers a
-    // link to the web version.
+    // External plugins are native dynamic libraries and the web build is
+    // already in the browser, so both actions are desktop-only.
     #[cfg(not(target_arch = "wasm32"))]
     {
+        secondary_items.push(outline_btn("Plugins", Message::PluginManagerOpen).into());
         // Filled with the active theme's primary colour.
         secondary_items.push(
             button(text("OCS Web").size(14))