refactor(rules): group focused security rules

shared/rules/security/references/network.md

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+# Network and SSRF security
+
+* Use HTTPS and never disable certificate or TLS validation.
+* Restrict inbound and outbound access to required ports, interfaces, hosts, and protocols.
+* Treat user-controlled URLs as dangerous: allowlist schemes and hosts, block localhost, metadata, and internal ranges, and revalidate redirects.
+* Set timeouts, response-size limits, bounded retries, and cancellation for remote operations.