Add proxy configuration support to downloader and GUI

Introduces proxy and geo-verification proxy options to the downloader and GUI dialogs, allowing users to specify network proxies for downloads and geo-restricted content. Updates the DownloadThread and main app logic to pass and apply these proxy settings, and adds validation and status indicators in the custom options dialog.

src/core/ytsage_downloader.py

@@ -59,6 +59,8 @@ class DownloadThread(QThread):
         rate_limit=None,
         download_section=None,
         force_keyframes=False,
+        proxy_url=None,
+        geo_proxy_url=None,
     ) -> None:
         super().__init__()
         self.url = url
@@ -78,6 +80,8 @@ class DownloadThread(QThread):
         self.rate_limit = rate_limit
         self.download_section = download_section
         self.force_keyframes = force_keyframes
+        self.proxy_url = proxy_url
+        self.geo_proxy_url = geo_proxy_url
         self.paused = False
         self.cancelled = False
         self.process = None
@@ -156,6 +160,13 @@ class DownloadThread(QThread):
                     self.browser_cookies.split(":")[1] if ":" in self.browser_cookies else None,
                 )
 
+            # Add proxy settings if specified
+            if self.proxy_url:
+                ydl_opts_check["proxy"] = self.proxy_url
+            
+            if self.geo_proxy_url:
+                ydl_opts_check["geo_verification_proxy"] = self.geo_proxy_url
+
             if YT_DLP_AVAILABLE:
                 with yt_dlp.YoutubeDL(ydl_opts_check) as ydl:
                     info = ydl.extract_info(self.url, download=False)
@@ -324,6 +335,13 @@ class DownloadThread(QThread):
         elif self.browser_cookies:
             cmd.extend(["--cookies-from-browser", self.browser_cookies])
 
+        # Add proxy settings if specified
+        if self.proxy_url:
+            cmd.extend(["--proxy", self.proxy_url])
+        
+        if self.geo_proxy_url:
+            cmd.extend(["--geo-verification-proxy", self.geo_proxy_url])
+
         # Add rate limit if specified
         if self.rate_limit:
             cmd.extend(["-r", self.rate_limit])