fix: route searx and alert SearXNG traffic through SOCKS5 proxy

Both plugins called urllib.request.urlopen directly, bypassing the
proxy. Switch to derp.http.urlopen and update the SearXNG endpoint
to the public domain (searx.mymx.me). Update test mocks to match.

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

plugins/searx.py

@@ -6,11 +6,12 @@ import json
 import urllib.parse
 import urllib.request
 
+from derp.http import urlopen as _urlopen
 from derp.plugin import command
 
 # -- Constants ---------------------------------------------------------------
 
-_SEARX_URL = "http://192.168.122.119:3000/search"
+_SEARX_URL = "https://searx.mymx.me/search"
 _FETCH_TIMEOUT = 10
 _MAX_RESULTS = 3
 _MAX_TITLE_LEN = 80
@@ -38,7 +39,7 @@ def _search(query: str) -> list[dict]:
     url = f"{_SEARX_URL}?{params}"
 
     req = urllib.request.Request(url, method="GET")
-    resp = urllib.request.urlopen(req, timeout=_FETCH_TIMEOUT)
+    resp = _urlopen(req, timeout=_FETCH_TIMEOUT)
     raw = resp.read()
     resp.close()