feat(proxy): refactor proxy configuration and add DataImpulse provider

- Updated proxy configuration in `.env.example` files to use `PROXY_URL` and `PROXY_URLS` instead of `CUSTOM_PROXY_URL` and `CUSTOM_PROXY_URLS`.
- Introduced `DataImpulseProvider` for proxy management, replacing the deprecated `AnonymousProxiesProvider`.
- Enhanced documentation to reflect changes in proxy setup and usage.
- Adjusted related code in the proxy registry and configuration files to support the new provider structure.

docker/.env.example

@@ -467,12 +467,15 @@ NOLOGIN_MODE_ENABLED=FALSE
 # Connector indexing lock TTL in seconds (default: 28800 = 8 hours)
 # CONNECTOR_INDEXING_LOCK_TTL_SECONDS=28800
 
-# Residential proxy for web crawling
-# RESIDENTIAL_PROXY_USERNAME=
-# RESIDENTIAL_PROXY_PASSWORD=
-# RESIDENTIAL_PROXY_HOSTNAME=
-# RESIDENTIAL_PROXY_LOCATION=
-# RESIDENTIAL_PROXY_TYPE=1
+# Proxy provider selection: "custom" (default) or "dataimpulse".
+# PROXY_PROVIDER=custom
+
+# Proxy endpoint(s), shared across providers. PROXY_URL is a single full URL used
+# by every provider (for "dataimpulse", country is a "__cr.<country>" username
+# suffix the provider parses for geoip). PROXY_URLS is a comma-separated pool the
+# "custom" provider rotates client-side. Leave unset to disable proxying.
+# PROXY_URL=http://user:pass@host:port
+# PROXY_URLS=http://user:pass@host1:port,http://user:pass@host2:port
 
 # ==============================================================================
 # DEV / DEPS-ONLY COMPOSE OVERRIDES