fix: poll Replicate for DeepSeek-R1 async predictions (202 Accepted)

DeepSeek-R1 is too slow for synchronous Replicate wait; it returns 202
with a prediction URL instead of the completed output. Added polling loop:
- POST with Prefer: wait=60
- If 202 or status=starting/processing, poll urls.get every 2s up to 90×
  (~3 min ceiling)
- On succeeded, use the final response data as normal
- On failed/canceled/timeout, log and return []
Also guards against output=None before calling str.join().

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/prescreener.py

@@ -221,7 +221,11 @@ def _parse_classify_output(raw: str) -> list[dict]:
 
 
 async def classify_with_deepseek(live_items: list[dict]) -> list[dict]:
-    """Single DeepSeek call → list of {domain, niche, type}."""
+    """Single DeepSeek call → list of {domain, niche, type}.
+
+    Replicate may return 202 (async) for slow models like DeepSeek-R1.
+    We poll the prediction URL until it succeeds or times out.
+    """
     if not live_items:
         return []
     payload = {
@@ -231,23 +235,49 @@ async def classify_with_deepseek(live_items: list[dict]) -> list[dict]:
             "temperature": 0.1,
         }
     }
+    auth_headers = {
+        "Authorization": f"Bearer {REPLICATE_TOKEN}",
+        "Content-Type": "application/json",
+    }
     try:
-        async with httpx.AsyncClient(timeout=120) as client:
+        async with httpx.AsyncClient(timeout=300) as client:
             resp = await client.post(
                 DEEPSEEK_MODEL,
-                headers={
+                headers={**auth_headers, "Prefer": "wait=60"},
-                    "Authorization": f"Bearer {REPLICATE_TOKEN}",
-                    "Content-Type": "application/json",
-                    "Prefer": "wait",
-                },
                 json=payload,
             )
             resp.raise_for_status()
             data = resp.json()
 
-        output = data.get("output", "")
+            # ── Poll if Replicate accepted async (202 or status starting/processing) ──
+            if resp.status_code == 202 or data.get("status") in ("starting", "processing"):
+                poll_url = (data.get("urls") or {}).get("get")
+                if not poll_url:
+                    logger.error("DeepSeek: 202 but no poll URL in response")
+                    return []
+                logger.info("DeepSeek: async prediction, polling %s", poll_url)
+                for attempt in range(90):          # up to ~3 minutes
+                    await asyncio.sleep(2)
+                    pr = await client.get(
+                        poll_url,
+                        headers={"Authorization": f"Bearer {REPLICATE_TOKEN}"},
+                    )
+                    pdata = pr.json()
+                    status = pdata.get("status")
+                    logger.debug("DeepSeek poll #%d status=%s", attempt + 1, status)
+                    if status == "succeeded":
+                        data = pdata
+                        break
+                    if status in ("failed", "canceled"):
+                        logger.error("DeepSeek prediction %s: %s", status, pdata.get("error"))
+                        return []
+                else:
+                    logger.error("DeepSeek: prediction timed out after polling 90×2s")
+                    return []
+
+        output = data.get("output") or ""
         if isinstance(output, list):
-            output = "".join(output)
+            output = "".join(str(t) for t in output if t is not None)
 
         logger.info("DeepSeek raw output (first 500 chars): %.500s", output)
         result = _parse_classify_output(output)