feat(forwarder/sniffer): add HTTP request body rewriting, deprecate rewriteBody in favor of rewriteResponseBody

- Add RewriteRequestBody field to HTTPNodeConfig (yaml: rewriteRequestBody)
- Add RewriteRequestBody field to HTTPNodeSettings in core chain
- Add rewriteReqBody function symmetric to rewriteRespBody in sniffer_rewrite.go
- Wire up rewriteReqBody call in httpRoundTrip before body wrapping for recording
- Add new RewriteResponseBody config field, deprecate old RewriteBody
- Parse both RewriteRequestBody and RewriteResponseBody in node config parsing
- Add 10 test cases covering nil, skip, content-type filter, and chained rewrites
- Bump core dependency to v0.4.1
- Fix: clone response header map in internal/util/sniffing/sniffer_http.go

config/config.go

@@ -417,8 +417,13 @@ type HTTPNodeConfig struct {
 	Rewrite []HTTPURLRewriteConfig `yaml:",omitempty" json:"rewrite,omitempty"`
 	// rewrite URL
 	RewriteURL []HTTPURLRewriteConfig `yaml:"rewriteURL,omitempty" json:"rewriteURL,omitempty"`
-	// rewrite response body
+	// Deprecated: use rewriteResponseBody instead
 	RewriteBody []HTTPBodyRewriteConfig `yaml:"rewriteBody,omitempty" json:"rewriteBody,omitempty"`
+	// rewrite request body
+	RewriteRequestBody []HTTPBodyRewriteConfig `yaml:"rewriteRequestBody,omitempty" json:"rewriteRequestBody,omitempty"`
+	// rewrite response body
+	RewriteResponseBody []HTTPBodyRewriteConfig `yaml:"rewriteResponseBody,omitempty" json:"rewriteResponseBody,omitempty"`
+
 	// HTTP basic auth
 	Auth *AuthConfig `yaml:",omitempty" json:"auth,omitempty"`
 }