feat: make SOCKS5 proxy configurable per adapter

Add `proxy` config option to server (IRC), teams, telegram, and mumble
sections. IRC defaults to false (preserving current direct-connect
behavior); all others default to true. The `derp.http` module now
accepts `proxy=True/False` on urlopen, create_connection,
open_connection, and build_opener -- when false, uses stdlib directly.

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

tests/test_config.py

@@ -280,3 +280,19 @@ class TestBuildServerConfigs:
         assert len(result) == 1
         name = list(result.keys())[0]
         assert result[name] is raw
+
+
+class TestProxyDefaults:
+    """Verify proxy defaults in each adapter section."""
+
+    def test_server_proxy_default_false(self):
+        assert DEFAULTS["server"]["proxy"] is False
+
+    def test_teams_proxy_default_true(self):
+        assert DEFAULTS["teams"]["proxy"] is True
+
+    def test_telegram_proxy_default_true(self):
+        assert DEFAULTS["telegram"]["proxy"] is True
+
+    def test_mumble_proxy_default_true(self):
+        assert DEFAULTS["mumble"]["proxy"] is True