feat(insta): dedup_window_days config end-to-end wiring (spec 6.4)

- insta-lab ranked_keywords: add dedup_window_days Query param (default 14, ge=1, le=90); pass to db.list_recent_issued_topics
- service_proxy.insta_ranked: add dedup_window_days param (default 14); include in GET params
- InstaAgent.on_schedule: read dedup_window_days from custom_config (default 14); pass to insta_ranked call
- test_ranked_respects_dedup_window: verifies window param gates eligible flag correctly

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

agent-office/app/service_proxy.py

@@ -228,11 +228,11 @@ async def insta_put_preferences(weights: Dict[str, float]) -> Dict[str, Any]:
     return resp.json()
 
 
-async def insta_ranked(threshold: float = 0.6, limit: int = 20) -> list:
+async def insta_ranked(threshold: float = 0.6, limit: int = 20, dedup_window_days: int = 14) -> list:
     async with httpx.AsyncClient(timeout=120) as client:
         r = await client.get(
             f"{INSTA_LAB_URL}/api/insta/keywords/ranked",
-            params={"threshold": threshold, "limit": limit},
+            params={"threshold": threshold, "limit": limit, "dedup_window_days": dedup_window_days},
         )
         r.raise_for_status()
         return r.json()["items"]