fix(companion): skip inv-sig-helper when Invidious Companion is enabled

- parser: skip decrypt_signature/decrypt_nsig when CONFIG.invidious_companion.present?

- youtube_api: avoid signatureTimestamp (STS) lookup under Companion

Aligns with the deprecation of inv-sig-helper in favor of Invidious Companion. No behavior change when Companion is disabled.

Refs: iv-org/invidious#5423

src/invidious/videos/parser.cr

@@ -542,14 +542,25 @@ private def convert_url(fmt)
 
     LOGGER.debug("convert_url: Decoding '#{cfr}'")
 
-    unsig = DECRYPT_FUNCTION.try &.decrypt_signature(cfr["s"])
+    # When using Invidious Companion, streaming URLs should already be usable.
+    # Skip inv-sig-helper based signature decryption in that case.
+    unsig = if CONFIG.invidious_companion.present?
+              nil
+            else
+              DECRYPT_FUNCTION.try &.decrypt_signature(cfr["s"])
+            end
     params[sp] = unsig if unsig
   else
     url = URI.parse(fmt["url"].as_s)
     params = url.query_params
   end
 
-  n = DECRYPT_FUNCTION.try &.decrypt_nsig(params["n"])
+  # Skip nsig decryption when using Invidious Companion
+  n = if CONFIG.invidious_companion.present?
+        nil
+      else
+        DECRYPT_FUNCTION.try &.decrypt_nsig(params["n"])
+      end
   params["n"] = n if n
 
   if token = CONFIG.po_token

src/invidious/yt_backend/youtube_api.cr

@@ -473,8 +473,12 @@ module YoutubeAPI
     } of String => String | Int64
 
     if {"WEB", "TVHTML5"}.any? { |s| client_config.name.starts_with? s }
-      if sts = DECRYPT_FUNCTION.try &.get_sts
-        playback_ctx["signatureTimestamp"] = sts.to_i64
+      # When using Invidious Companion, player requests are proxied there,
+      # so we skip fetching signatureTimestamp via inv-sig-helper.
+      if !CONFIG.invidious_companion.present?
+        if sts = DECRYPT_FUNCTION.try &.get_sts
+          playback_ctx["signatureTimestamp"] = sts.to_i64
+        end
       end
     end