fix: retry transient SSL/connection errors in alert backends

Add retry loop (3 attempts, exponential backoff) for SSLError,
ConnectionError, TimeoutError, and OSError in alert poll cycle.
Non-transient errors fail immediately. Also fixes searx test
mocks to match direct urlopen usage.

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

plugins/alert.py

@@ -5,6 +5,7 @@ from __future__ import annotations
 import asyncio
 import json
 import re
+import ssl
 import urllib.request
 from datetime import datetime, timezone
 
@@ -271,11 +272,22 @@ async def _poll_once(bot, key: str, announce: bool = True) -> None:
     loop = asyncio.get_running_loop()
 
     for tag, backend in _BACKENDS.items():
-        try:
-            items = await loop.run_in_executor(None, backend, keyword)
-        except Exception as exc:
-            data["last_error"] = f"{tag}: {exc}"
-            had_error = True
+        items = None
+        for attempt in range(3):
+            try:
+                items = await loop.run_in_executor(None, backend, keyword)
+                break
+            except (ssl.SSLError, ConnectionError, TimeoutError, OSError) as exc:
+                if attempt < 2:
+                    await asyncio.sleep(2 ** attempt)
+                    continue
+                data["last_error"] = f"{tag}: {exc}"
+                had_error = True
+            except Exception as exc:
+                data["last_error"] = f"{tag}: {exc}"
+                had_error = True
+                break
+        if items is None:
             continue
 
         seen_set = set(data.get("seen", {}).get(tag, []))