feat: add web search tool using SearXNG

Add WebSearchTool that queries the self-hosted SearXNG metasearch engine
for current information, documentation, and facts beyond training data.

- Add SEARXNG_URL and SEARXNG_TIMEOUT config settings
- Create WebSearchTool with query, num_results, categories params
- Register web_search tool with explore agent
- Add 10 tests for search functionality

Usage: Agents can now use web_search(query="...") to find current info.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

webber-api/src/domains/agents/explore/tools.py

@@ -11,6 +11,7 @@ from src.domains.tools.file.glob import GlobFilesTool
 from src.domains.tools.file.edit import EditFileTool
 from src.domains.tools.file.write import WriteFileTool
 from src.domains.tools.search.grep import GrepContentTool
+from src.domains.tools.search.web import WebSearchTool
 from src.domains.tools.shell.bash import BashReadOnlyTool
 from src.domains.tools.shell.bash_full import BashTool
 
@@ -271,3 +272,42 @@ def register_explore_tools(agent: Agent[AgentContext, str]) -> None:
             timeout=min(timeout, ctx.deps.timeout_seconds)
         )
         return result.to_string()
+
+    # === Web search ===
+
+    @agent.tool
+    async def web_search(
+        ctx: RunContext[AgentContext],
+        query: str,
+        num_results: int = 5,
+        categories: str | None = None
+    ) -> str:
+        """Search the web for current information.
+
+        Args:
+            query: Search query (e.g., "Python 3.12 new features")
+            num_results: Number of results to return (1-10, default: 5)
+            categories: Optional category filter ("general", "it", "news", "science")
+
+        Returns:
+            Search results with titles, URLs, and snippets.
+
+        Use this for:
+        - Current events or recent information
+        - Documentation updates since your training
+        - Facts you're uncertain about
+        - Technical references with URLs
+
+        IMPORTANT: Always include a "Sources:" section with URLs in your response.
+
+        Examples:
+            - query="FastAPI best practices 2024"
+            - query="CVE-2024" categories="it"
+        """
+        tool = WebSearchTool()
+        result = await tool.execute(
+            query=query,
+            num_results=num_results,
+            categories=categories
+        )
+        return result.to_string()