feat(parsers): add SOAP API support for zakupki.gov.ru

- Add post() method to BaseHTTPClient for SOAP requests
- Update download_file() to support custom headers (for token)
- Add ZAKUPKI_TOKEN and PARSER_PROXIES settings
- Improve SOAP error parsing to show EIS error messages
- Update E2E tests to use token from settings
- Add data/ and .zed/ to gitignore

.env.example

@@ -28,4 +28,8 @@ CORS_ALLOWED_ORIGINS=http://localhost:3000,http://127.0.0.1:3000
 LOG_LEVEL=INFO
 
 # Scrapy Settings
-SCRAPY_LOG_LEVEL=INFO
+SCRAPY_LOG_LEVEL=INFO
+
+# Parsers API Tokens
+# Токен для zakupki.gov.ru (получить через Госуслуги на https://zakupki.gov.ru/pmd/auth/welcome)
+ZAKUPKI_TOKEN=