Add Brave Search web search to OpenClaw

- Enable web_search tool with Brave provider
- Add openclaw_brave_api_key secret to SOPS configuration
- Add BRAVE_API_KEY to openclaw.env template

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

modules/openclaw-config.json

@@ -29,7 +29,14 @@
   },
   "tools": {
     "elevated": { "enabled": true },
-    "exec": { "security": "full", "ask": "off" }
+    "exec": { "security": "full", "ask": "off" },
+    "web": {
+      "search": {
+        "enabled": true,
+        "provider": "brave",
+        "apiKey": "${BRAVE_API_KEY}"
+      }
+    }
   },
   "models": {
     "providers": {