Enhance API path normalization and configuration validation

- Introduced a new function to normalize request URL paths, collapsing duplicate slashes and clearing raw paths to ensure correct routing in the reverse proxy.
- Updated the gateway to utilize the normalization function for API requests, improving routing consistency.
- Trimmed whitespace from server configuration fields in the validation process to prevent potential issues with malformed URLs.
- Enhanced documentation in GATEWAY_RUN.md to clarify the importance of proper URL formatting and configuration.

internal/config/config.go

@@ -75,6 +75,10 @@ func (c *Config) Validate() error {
 	seen := make(map[string]struct{})
 	for i := range c.Servers {
 		s := &c.Servers[i]
+		s.Alias = strings.TrimSpace(s.Alias)
+		s.BaseURL = strings.TrimSpace(s.BaseURL)
+		s.PathPrefix = strings.TrimSpace(s.PathPrefix)
+		s.AuthorizationEnv = strings.TrimSpace(s.AuthorizationEnv)
 		if s.Alias == "" {
 			return fmt.Errorf("servers[%d]: alias is required", i)
 		}