Add SOCKS5 and HTTP/HTTPS proxy support

- Updated `GetAuthenticatedClient` to handle proxy configuration via `proxy-url`.
- Extended `Config` to include `proxy-url` property.
- Adjusted error handling and removed unused JSON error response logic for API handlers.
- Updated documentation and configuration examples to reflect new proxy settings.

internal/config/config.go

@@ -8,10 +8,11 @@ import (
 
 // Config represents the application's configuration
 type Config struct {
-	Port    int      `yaml:"port"`
-	AuthDir string   `yaml:"auth_dir"`
-	Debug   bool     `yaml:"debug"`
-	ApiKeys []string `yaml:"api_keys"`
+	Port     int      `yaml:"port"`
+	AuthDir  string   `yaml:"auth_dir"`
+	Debug    bool     `yaml:"debug"`
+	ProxyUrl string   `yaml:"proxy-url"`
+	ApiKeys  []string `yaml:"api_keys"`
 }
 
 // / LoadConfig loads the configuration from the specified file