api: add local processing response type & param

`local-processing` type returns needed info for on-device processing and creates basic proxy tunnels

api/src/processing/schema.js

@@ -36,16 +36,14 @@ export const apiSchema = z.object({
                      .regex(/^[0-9a-zA-Z\-]+$/)
                      .optional(),
 
-    // TODO: remove this variable as it's no longer used
-    // and is kept for schema compatibility reasons
-    youtubeDubBrowserLang: z.boolean().default(false),
-
-    alwaysProxy: z.boolean().default(false),
     disableMetadata: z.boolean().default(false),
     tiktokFullAudio: z.boolean().default(false),
     tiktokH265: z.boolean().default(false),
     twitterGif: z.boolean().default(true),
 
+    alwaysProxy: z.boolean().default(false),
+    localProcessing: z.boolean().default(false),
+
     youtubeHLS: z.boolean().default(false),
 })
 .strict();