perf: add HTTP connection pooling across providers and disable proxy buffering on SSE streams

internal/providers/moonshot.go

@@ -21,7 +21,7 @@ type MoonshotProvider struct {
 
 func NewMoonshotProvider(cfg config.MoonshotConfig, apiKey string) *MoonshotProvider {
 	return &MoonshotProvider{
-		client: resty.New().SetTimeout(10 * time.Minute),
+		client: NewOptimizedRestyClient(10 * time.Minute),
 		config: cfg,
 		apiKey: strings.TrimSpace(apiKey),
 	}