feat(08-03): create CrawlerConfig for proxy and rate limiting

- Add CrawlerConfig with ProxyConfig, delay, and retry settings
- Support HTTP_PROXY/HTTPS_PROXY environment variable parsing
- Add proxy_required validation with clear error message
- Add get_crawler_config singleton for configuration access

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

tests/test_crawler/test_proxy_config.py

@@ -0,0 +1,125 @@
+"""Tests for Crawler Proxy Configuration"""
+
+import os
+import pytest
+from unittest.mock import patch
+
+from kb_workflow.crawler.config import (
+    CrawlerConfig,
+    ProxyConfig,
+    get_crawler_config,
+    reset_crawler_config,
+)
+
+
+class TestProxyConfig:
+    """Tests for ProxyConfig model."""
+
+    def test_parse_proxy_from_https_env(self):
+        """Parse proxy from HTTPS_PROXY environment variable."""
+        reset_crawler_config()
+        with patch.dict(os.environ, {"HTTPS_PROXY": "http://127.0.0.1:7890"}, clear=False):
+            os.environ.pop("HTTP_PROXY", None)
+            config = CrawlerConfig.from_env()
+            assert config.proxy is not None
+            assert config.proxy.server == "http://127.0.0.1:7890"
+
+    def test_parse_proxy_from_http_env(self):
+        """Parse proxy from HTTP_PROXY (HTTPS_PROXY takes priority)."""
+        reset_crawler_config()
+        with patch.dict(os.environ, {
+            "HTTP_PROXY": "http://127.0.0.1:8080",
+            "HTTPS_PROXY": "http://127.0.0.1:7890"
+        }, clear=False):
+            config = CrawlerConfig.from_env()
+            assert config.proxy.server == "http://127.0.0.1:7890"
+
+    def test_parse_proxy_with_auth(self):
+        """Parse proxy with authentication credentials."""
+        reset_crawler_config()
+        with patch.dict(os.environ, {
+            "HTTPS_PROXY": "http://user:pass@proxy.example.com:8080"
+        }, clear=False):
+            os.environ.pop("HTTP_PROXY", None)
+            config = CrawlerConfig.from_env()
+            assert config.proxy.username == "user"
+            assert config.proxy.password == "pass"
+            assert config.proxy.server == "http://proxy.example.com:8080"
+
+    def test_no_proxy_configured(self):
+        """Handle case when no proxy is configured."""
+        reset_crawler_config()
+        # Save current values
+        old_http = os.environ.get("HTTP_PROXY")
+        old_https = os.environ.get("HTTPS_PROXY")
+
+        try:
+            os.environ.pop("HTTP_PROXY", None)
+            os.environ.pop("HTTPS_PROXY", None)
+            config = CrawlerConfig.from_env()
+            assert config.proxy is None
+        finally:
+            # Restore
+            if old_http:
+                os.environ["HTTP_PROXY"] = old_http
+            if old_https:
+                os.environ["HTTPS_PROXY"] = old_https
+
+    def test_proxy_required_validation_fails(self):
+        """Raise ValueError when proxy required but not configured."""
+        config = CrawlerConfig(proxy=None, proxy_required=True)
+        with pytest.raises(ValueError, match="Proxy configuration missing"):
+            config.validate_proxy()
+
+    def test_proxy_required_validation_passes(self):
+        """Pass validation when proxy is configured and required."""
+        config = CrawlerConfig(
+            proxy=ProxyConfig(server="http://127.0.0.1:7890"),
+            proxy_required=True
+        )
+        # Should not raise exception
+        config.validate_proxy()
+
+    def test_proxy_not_required(self):
+        """Pass validation when proxy is not required."""
+        config = CrawlerConfig(proxy=None, proxy_required=False)
+        # Should not raise exception
+        config.validate_proxy()
+
+    def test_to_playwright_format(self):
+        """Convert to Playwright proxy format."""
+        proxy = ProxyConfig(
+            server="http://127.0.0.1:7890",
+            username="user",
+            password="pass"
+        )
+        result = proxy.to_playwright_format()
+        assert result == {
+            "server": "http://127.0.0.1:7890",
+            "username": "user",
+            "password": "pass"
+        }
+
+    def test_to_playwright_format_no_auth(self):
+        """Convert to Playwright format without authentication."""
+        proxy = ProxyConfig(server="http://127.0.0.1:7890")
+        result = proxy.to_playwright_format()
+        assert result == {"server": "http://127.0.0.1:7890"}
+
+    def test_get_crawler_config_singleton(self):
+        """Test that get_crawler_config returns cached instance."""
+        reset_crawler_config()
+        with patch.dict(os.environ, {"HTTPS_PROXY": "http://127.0.0.1:7890"}, clear=False):
+            os.environ.pop("HTTP_PROXY", None)
+            config1 = get_crawler_config()
+            config2 = get_crawler_config()
+            assert config1 is config2
+
+    def test_default_values(self):
+        """Test default configuration values."""
+        config = CrawlerConfig(proxy=None, proxy_required=False)
+        assert config.min_delay == 1.0
+        assert config.max_delay == 3.0
+        assert config.max_retries == 3
+        assert config.retry_min_wait == 2.0
+        assert config.retry_max_wait == 10.0