Default-secure: localhost bind, enforce mode, apple-container backend

[persimmon16]

Summary

• F02: Bridge daemon binds 127.0.0.1 instead of 0.0.0.0
• F08: Gateway binds 127.0.0.1:8080 instead of 0.0.0.0:8080
• F09: L7 policy enforcement defaults to Enforce (deny) instead of Audit (pass-through)
• F13: Sandbox backend defaults to apple-container instead of kubernetes

Breaking: Deployments relying on remote access must now explicitly pass --host 0.0.0.0 (bridge) or set a bind address (gateway). Policies without an explicit enforcement field now block violations instead of logging them.

Test plan

• cargo build --release succeeds
• Gateway starts and binds to 127.0.0.1:8080
• Bridge starts and binds to 127.0.0.1:50052