fix: replay idempotent upload token safely

apps/api/app/main.py

@@ -478,7 +478,12 @@ def create_catch_report(
             report = existing.catch_report
             if report is None:
                 raise HTTPException(status_code=409, detail="idempotency record is incomplete; retry with a new key")
-            return JSONResponse(status_code=200, content={"id": str(report.id), "moderation_status": report.moderation_status.value, "screenshot_upload_token": "", "idempotent": True})
+            # Re-derive the one-time upload token from the idempotency key;
+            # only its hash is persisted, so the secret is never stored.
+            replay_token = hmac.new(settings.rate_limit_secret.encode(), (key_hash + ":upload").encode(), hashlib.sha256).hexdigest()
+            if not hmac.compare_digest(hashlib.sha256(replay_token.encode()).hexdigest(), report.screenshot_upload_token_hash or ""):
+                raise HTTPException(status_code=409, detail="idempotency record token mismatch; retry with a new key")
+            return JSONResponse(status_code=200, content={"id": str(report.id), "moderation_status": report.moderation_status.value, "screenshot_upload_token": replay_token, "idempotent": True})
         logger.info("idempotency check miss", extra={"idempotency_key": idempotency_key[:8]})
     _check_rate_limit(request, db)
     fish = db.scalar(select(Fish).where(Fish.slug == payload.fish_slug))
@@ -496,7 +501,8 @@ def create_catch_report(
         if bait is None:
             bait = Bait(name=payload.bait_name.strip(), normalized_name=key, kind=BaitKind.unknown)
             db.add(bait)
-    upload_token = secrets.token_urlsafe(32)
+    upload_token = (hmac.new(settings.rate_limit_secret.encode(), (key_hash + ":upload").encode(), hashlib.sha256).hexdigest()
+                    if idempotency_key else secrets.token_urlsafe(32))
     report = CatchReport(fish=fish, spot=spot, waterbody=waterbody, bait=bait, weight_g=payload.weight_g, fishing_method=payload.fishing_method, rig_type=payload.rig_type, retrieve_method=payload.retrieve_method, retrieve_speed=payload.retrieve_speed, caught_at=payload.caught_at, reported_at=datetime.now(timezone.utc), player_name=payload.player_name, source_type=SourceType.user, source_url=payload.source_url, source_confidence=60, moderation_status=ModerationStatus.pending, raw_payload={"comment": payload.comment} if payload.comment else None, screenshot_upload_token_hash=hashlib.sha256(upload_token.encode()).hexdigest())
     db.add(report)
     db.commit()