Bind task_showcase to 127.0.0.1 by default

[Harun Khan (harunkkhan)]

Fixes #72.

assets/task_showcase/app.py defaulted --host to 0.0.0.0, exposing the showcase on every network interface, while both READMEs document http://127.0.0.1:5005. This changes the default to 127.0.0.1 and adds a line to assets/task_showcase/README.md noting that --host 0.0.0.0 exposes it on the network.

Note: this is a behavior change for anyone who relied on the old default to reach the showcase from another machine; they now need to pass --host 0.0.0.0 explicitly. The internal launcher in src/cuawright/webwright/config/task_showcase.yaml already passes --host 127.0.0.1 and is unaffected. PR #67 also touches app.py (different lines); happy to rebase if it lands first.

Testing: ran python app.py with no arguments; lsof shows it listening only on 127.0.0.1:5005 and / returns 200.

[Harun Khan (harunkkhan)]

@microsoft-github-policy-service agree