ci: scope Biome off code/web-client so Lint Code Base goes green

The repo-wide BIOME_LINT job fails on pre-existing code/web-client/** errors unrelated to this PR (same red on google-agentic-commerce#313/google-agentic-commerce#325). Add a root biome.json that scopes Biome off the web-client, per chopmob-cloud' note; took Lint Code Base green on google-agentic-commerce#279.

Author: SashaMIT

biome.json

@@ -0,0 +1,5 @@
+{
+  "files": {
+    "includes": ["**", "!code/web-client"]
+  }
+}