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/server/gateway.go

@@ -228,6 +228,10 @@ func (g *Gateway) serve(w http.ResponseWriter, r *http.Request) {
 		g.promHandler.ServeHTTP(w, r)
 		return
 	}
+	// So /api//mtg/health and /api/../api/agg/... route like /api/mtg/health and /api/agg/...
+	if strings.HasPrefix(r.URL.Path, "/api") {
+		proxy.NormalizeRequestURLPath(r)
+	}
 	const prefix = "/api/"
 	if r.URL.Path == "/api/agg" || strings.HasPrefix(r.URL.Path, "/api/agg/") {
 		g.agg.ServeHTTP(w, r)