web: updated api endpoint & params, default instance override

- dialogs can be undismissable now (impossible to click away by pressing the bg behind it)
- added security warning about api override
- moved default api url to env
- added new processing settings page

web/src/lib/settings/defaults.ts

@@ -28,7 +28,11 @@ const defaultSettings: CobaltSettings = {
         youtubeDubBrowserLang: false,
     },
     privacy: {
-        disableAnalytics: false
+        disableAnalytics: false,
+    },
+    processing: {
+        allowDefaultOverride: false,
+        seenOverrideWarning: false,
     }
 }