feat: add dead proxy reporting to source API

When report_url is configured, POST evicted proxy list as JSON after
each health test cycle. Fire-and-forget: failures are logged at debug
level. Payload format: {"dead": [{"proto": "socks5", "proxy": "host:port"}]}.

tests/test_pool.py

@@ -257,6 +257,70 @@ class TestProxyPoolHealthTests:
         assert pool._proxies["socks5://10.0.0.1:1080"].alive is True
 
 
+class TestProxyPoolReport:
+    """Test dead proxy reporting."""
+
+    def test_report_called_on_eviction(self):
+        import asyncio
+        from unittest.mock import AsyncMock, patch
+
+        cfg = ProxyPoolConfig(sources=[], report_url="http://api:8081/report", max_fails=1)
+        pool = ProxyPool(cfg, [], timeout=10.0)
+
+        now = time.time()
+        hop = ChainHop(proto="socks5", host="10.0.0.1", port=1080)
+        pool._proxies["socks5://10.0.0.1:1080"] = ProxyEntry(
+            hop=hop, alive=False, last_seen=now, fails=0,
+        )
+
+        with (
+            patch.object(pool, "_test_proxy", new_callable=AsyncMock, return_value=False),
+            patch.object(pool, "_report_dead", new_callable=AsyncMock) as mock_report,
+        ):
+            asyncio.run(pool._run_health_tests())
+            # proxy should be evicted (fails=1 >= max_fails=1)
+            assert "socks5://10.0.0.1:1080" not in pool._proxies
+            mock_report.assert_called_once()
+            keys = mock_report.call_args[0][0]
+            assert "socks5://10.0.0.1:1080" in keys
+
+    def test_report_not_called_without_url(self):
+        import asyncio
+        from unittest.mock import AsyncMock, patch
+
+        cfg = ProxyPoolConfig(sources=[], max_fails=1)  # no report_url
+        pool = ProxyPool(cfg, [], timeout=10.0)
+
+        now = time.time()
+        hop = ChainHop(proto="socks5", host="10.0.0.1", port=1080)
+        pool._proxies["socks5://10.0.0.1:1080"] = ProxyEntry(
+            hop=hop, alive=False, last_seen=now, fails=0,
+        )
+
+        with (
+            patch.object(pool, "_test_proxy", new_callable=AsyncMock, return_value=False),
+            patch.object(pool, "_report_dead", new_callable=AsyncMock) as mock_report,
+        ):
+            asyncio.run(pool._run_health_tests())
+            mock_report.assert_not_called()
+
+    def test_report_sync_payload(self):
+        from unittest.mock import MagicMock, patch
+
+        cfg = ProxyPoolConfig(sources=[], report_url="http://api:8081/report")
+        pool = ProxyPool(cfg, [], timeout=10.0)
+
+        dead = [{"proto": "socks5", "proxy": "10.0.0.1:1080"}]
+        with patch("s5p.pool.urllib.request.urlopen", new_callable=MagicMock) as mock_open:
+            mock_open.return_value.__enter__ = MagicMock()
+            mock_open.return_value.__exit__ = MagicMock(return_value=False)
+            pool._report_sync(dead)
+            req = mock_open.call_args[0][0]
+            assert req.method == "POST"
+            assert req.full_url == "http://api:8081/report"
+            assert b'"dead"' in req.data
+
+
 class TestProxyPoolStaleExpiry:
     """Test stale proxy eviction."""