feat: add retry logic for transient failures

- @with_retry decorator and retry_async() function
- Exponential backoff with jitter
- Retries on: timeout, connection errors, HTTP 429/5xx
- Web search tool now retries on network failures
- Configurable via RETRY_MAX_ATTEMPTS, RETRY_BASE_DELAY, RETRY_MAX_DELAY
- 29 new tests (205 total passing)

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

webber-api/src/domains/tools/search/web.py

@@ -9,6 +9,7 @@ import httpx
 from src.domains.tools.base import BaseTool, ToolResult
 from src.shared.config import get_settings
 from src.shared.logging import logged, get_logger
+from src.shared.retry import retry_async
 
 logger = get_logger(__name__)
 
@@ -73,6 +74,24 @@ IMPORTANT:
         self.searxng_url = (searxng_url or settings.searxng_url).rstrip("/")
         self.timeout = timeout or settings.searxng_timeout
         self.max_results = max_results
+        # Retry settings
+        self.retry_max_attempts = settings.retry_max_attempts
+        self.retry_base_delay = settings.retry_base_delay
+        self.retry_max_delay = settings.retry_max_delay
+
+    async def _fetch_search_results(self, params: dict) -> dict:
+        """
+        Fetch search results from SearXNG.
+
+        This method is wrapped with retry logic for transient failures.
+        """
+        async with httpx.AsyncClient(timeout=self.timeout) as client:
+            response = await client.get(
+                f"{self.searxng_url}/search",
+                params=params,
+            )
+            response.raise_for_status()
+            return response.json()
 
     @logged()
     async def execute(
@@ -111,16 +130,15 @@ IMPORTANT:
             params["categories"] = categories
 
         try:
-            async with httpx.AsyncClient(timeout=self.timeout) as client:
-                response = await client.get(
-                    f"{self.searxng_url}/search",
-                    params=params,
-                )
-                response.raise_for_status()
-                data = response.json()
-
+            data = await retry_async(
+                self._fetch_search_results,
+                params,
+                max_attempts=self.retry_max_attempts,
+                base_delay=self.retry_base_delay,
+                max_delay=self.retry_max_delay,
+            )
         except httpx.TimeoutException:
-            return self._error(f"Search timed out after {self.timeout}s")
+            return self._error(f"Search timed out after {self.timeout}s (all retries exhausted)")
         except httpx.HTTPStatusError as e:
             return self._error(f"Search failed: HTTP {e.response.status_code}")
         except httpx.RequestError as e: