fix(config): add missing base-claude.settings.json

The claude provider was fully registered in the codebase (types,
OAuth config, auth port 54545, model catalog, CLI routes) but the
required base config file was missing, causing "Base config not
found for provider 'claude'" error when running `ccs claude --add`.

config/base-claude.settings.json

@@ -0,0 +1,10 @@
+{
+  "env": {
+    "ANTHROPIC_BASE_URL": "http://127.0.0.1:8317/api/provider/claude",
+    "ANTHROPIC_AUTH_TOKEN": "ccs-internal-managed",
+    "ANTHROPIC_MODEL": "claude-sonnet-4-20250514",
+    "ANTHROPIC_DEFAULT_OPUS_MODEL": "claude-opus-4-20250514",
+    "ANTHROPIC_DEFAULT_SONNET_MODEL": "claude-sonnet-4-20250514",
+    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "claude-haiku-3-5-20241022"
+  }
+}