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/summarize.py

@@ -5,9 +5,9 @@ from __future__ import annotations
 import logging
 
 from us2kr.config import Settings
-from us2kr.llm.base import LLMProvider
+from us2kr.llm.base import LLMError, LLMProvider
 from us2kr.llm.minimax import MiniMaxProvider
-from us2kr.models import MarketPayload, Report
+from us2kr.models import MarketPayload, Report, Verification
 
 log = logging.getLogger(__name__)
 
@@ -28,3 +28,45 @@ def summarize_payload(payload: MarketPayload, provider: LLMProvider) -> tuple[Re
         report = report.model_copy(update={"data_gaps": merged})
     log.info("summary produced by %s (%d data gaps)", model_used, len(merged))
     return report, model_used
+
+
+def _consistent(verification: Verification) -> Verification:
+    """Force `ok` to mean "no major issues" - verifier models are inconsistent about minor-only cases."""
+    ok = not verification.has_major
+    return verification if verification.ok == ok else verification.model_copy(update={"ok": ok})
+
+
+def verify_and_revise(
+    payload: MarketPayload, report: Report, provider: LLMProvider
+) -> tuple[Report, Verification]:
+    """Fact-check the report; on major issues ask for one revision and re-check it.
+
+    Returns (possibly revised report, verification of the returned report). Raises LLMError only when
+    the *initial* verification cannot be produced; a failed revision keeps the original report.
+    """
+    raw_verification, model = provider.verify(payload, report)
+    verification = _consistent(raw_verification)
+    log.info(
+        "verification by %s: ok=%s issues=%d (major=%s)",
+        model,
+        verification.ok,
+        len(verification.issues),
+        verification.has_major,
+    )
+    if not verification.has_major:
+        return report, verification
+
+    for issue in verification.issues:
+        log.warning("verification issue [%s] %s -> %s", issue.severity, issue.claim, issue.problem)
+    try:
+        revised, model = provider.revise(payload, report, verification.issues)
+        log.info("report revised by %s after verification issues", model)
+        re_verification, model = provider.verify(payload, revised)
+        re_verification = _consistent(re_verification)
+        log.info(
+            "re-verification by %s: ok=%s issues=%d", model, re_verification.ok, len(re_verification.issues)
+        )
+        return revised, re_verification
+    except LLMError as exc:
+        log.warning("revision failed; keeping the original report and verdict: %s", exc)
+        return report, verification