[codex] Expose HTTP compression level setting

[Avilianb]

Summary

Expose the HTTP compression level setting in the content compression UI.

Root Cause

http-compression-config-box allowed users to enable content compression and choose Brotli/Gzip/ZSTD/Deflate, but the hidden level field defaulted to 0. EdgeNode only applies compression when Compression.IsOn && Compression.Level > 0, so an enabled UI state could still save a runtime-disabled compression config.

Changes

• Default new content compression configs to level: 2.
• Normalize missing or non-positive level values to 2 when rendering the config editor.
• Add a visible compression level selector to the content compression settings form.
• Bind the selector with v-model.number so the JSON payload preserves a numeric value.

Validation

• git diff --check
• node --check web/public/js/components/server/http-compression-config-box.js

go test ./... was attempted but the checkout reported that go.mod needs updates; I did not run go mod tidy because this PR only changes a frontend component.