Add URL validation and ytdlp error messages to translations

Added new translation keys for URL validation and ytdlp error messages in all supported languages. This improves error reporting and user feedback for invalid URLs and common download issues.

languages/en.json

@@ -398,5 +398,27 @@
     "next_check_error": "Next check: Error calculating",
     "checking": "🔄 Checking...",
     "check_now": "🔍 Check for Updates Now"
+  },
+  "url_validation": {
+    "empty_url": "URL cannot be empty",
+    "invalid_format": "Invalid URL format",
+    "invalid_scheme": "URL must start with http:// or https://",
+    "missing_domain": "Invalid URL: missing domain name",
+    "unsupported_platform": "YTSage only supports YouTube and YouTube Music URLs.\nThe domain '{domain}' is not supported.",
+    "invalid_youtu_be": "Invalid youtu.be URL: missing video ID"
+  },
+  "ytdlp_errors": {
+    "private_video": "This is a private video. You can download it by logging into your account using cookies.\nGo to 'Custom Options' → 'Login with Cookies' → 'Extract cookies from browser' to authenticate.",
+    "age_restricted": "This video is age-restricted. You need to be logged in to access it.\nUse 'Custom Options' → 'Login with Cookies' to authenticate with your account.",
+    "geo_blocked": "This video is not available in your region (geo-blocked).\nYou may need to use a VPN or the video might be restricted in your country.",
+    "video_unavailable": "This video has been removed or is no longer available.\nThe video may have been deleted by the uploader or removed due to policy violations.",
+    "live_stream": "This is a live stream that cannot be downloaded while active.\nWait for the stream to end, then try downloading the archived version.",
+    "playlist_error": "Unable to access this playlist. It may be private, deleted, or empty.\nCheck if the playlist exists and is publicly accessible.",
+    "network_error": "Network connection error. Please check your internet connection and try again.\nIf the problem persists, the video server might be temporarily unavailable.",
+    "invalid_url": "Invalid or unsupported URL. Please check the link and try again.\nMake sure you're using a valid YouTube, Vimeo, or other supported platform URL.",
+    "premium_content": "This content requires YouTube Premium or channel membership.\nYou need to be logged in with an account that has access to this content.",
+    "copyright_blocked": "This video is blocked due to copyright claims.\nThe content owner has restricted access to this video.",
+    "extraction_failed": "Failed to extract video information. This might be a temporary issue.\nPlease try again in a few minutes, or check if the video link is correct.",
+    "generic_error": "Could not extract video information. Please check your link.\nTechnical details: {error}"
   }
 }