Add resumable US policy news collectors and provenance

Collect official crypto and US policy documents with deterministic screening, full bodies and attachments, bounded retries, and durable history cursors. Preserve publication precision and source identity while keeping new collectors disabled.

Add real Congress, GovInfo, DOJ and Federal Register fixtures, offline capture replay, isolated database validation, and rollout instructions. Validate 982 backend tests, frontend checks, and 57 deployment control tests.

backend/src/alphapulse/core/config.py

@@ -7,6 +7,9 @@ class Settings(BaseSettings):
     # 容器内由 compose 的 env_file 注入；只有一套配置，见仓库根目录 .env
     model_config = SettingsConfigDict(extra="ignore")
 
+    congress_api_key: str = ""
+    crawler_contact_email: str = ""
+
     searxng_url: str = "http://searxng:8080"
     database_url: str
     redis_url: str