Add an LLM fact-check pass over the generated briefing

After summarisation the report is verified against the collected
payload (numbers, directions, unsupported claims) by a second LLM call
with a Verification JSON schema. Major issues trigger one revision and
a re-check; minor-only verdicts are normalized to ok. Failures never
block delivery. The verdict is stored in the result JSON and shown on
the dashboard (badge + 검증 메모). Disable with US2KR_VERIFY_ENABLED.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

us2kr/config.py

@@ -65,6 +65,9 @@ class Settings(BaseSettings):
     news_lookback_hours: int = Field(default=18, alias="US2KR_NEWS_LOOKBACK_HOURS")
     news_max_items: int = Field(default=40, alias="US2KR_NEWS_MAX_ITEMS")
 
+    # --- LLM verification (fact-check pass over the generated report) ---
+    verify_enabled: bool = Field(default=True, alias="US2KR_VERIFY_ENABLED")
+
     log_level: str = Field(default="INFO", alias="US2KR_LOG_LEVEL")
 
     @field_validator("minimax_fallback_models", "krx_extra_holidays", "searxng_queries", mode="before")