fix(scraper): always fetch newest posts first

Stop resuming from the persisted (older) BoxAPI cursor. Resuming made every
sync walk further back in time and never re-fetch posts published since the
last run, so a seller's newest posts were never imported. Always start from
max_id=None (newest) and page older within a single run, de-duping against
the DB: brand-new posts first, then older un-imported ones.

Also emit timezone-aware UTC created_at so ordering is correct regardless of
the container's local timezone (and Django no longer receives naive datetimes).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scraper.py

@@ -1,7 +1,7 @@
 # scraper.py
 import os
 from typing import List, Dict, Any, Optional, Tuple, Set
-from datetime import datetime
+from datetime import datetime, timezone
 
 from sqlalchemy.orm import Session
 from sqlalchemy import select
@@ -100,9 +100,14 @@ def scrape_and_store(db: Session, req: ScrapeRequest) -> List[ScrapedPost]:
     # Account (needed for saving)
     account = _get_or_create_account(db, username, req.seller_id)
 
-    # Cursor: start where we left off (older pages)
-    max_id: Optional[str] = _get_cursor(db, username)
-    dprint(f"start_cursor={max_id!r}")
+    # ALWAYS start from the newest page (max_id=None). We must not resume from a
+    # persisted "older" cursor: doing so makes every sync walk further back in
+    # time and never re-fetch posts published since the last run, so the seller's
+    # newest posts never get imported. BoxAPI returns newest-first and the parser
+    # sorts newest-first, so paging older within this single run and de-duping
+    # against the DB yields: brand-new posts first, then older un-imported ones.
+    max_id: Optional[str] = None
+    dprint(f"start_cursor={max_id!r} (forced newest-first)")
 
     # Page through BoxAPI until we collect enough NEW items (older than what we have)
     pages = 0
@@ -235,7 +240,14 @@ def scrape_and_store(db: Session, req: ScrapeRequest) -> List[ScrapedPost]:
             except Exception as e:
                 print(f"⚠️ Failed to upload thumbnail: {e}")
 
-        created_at = datetime.fromtimestamp(item["taken_at"]) if item.get("taken_at") else datetime.utcnow()
+        # taken_at is a Unix timestamp (UTC). Build a timezone-aware UTC datetime
+        # so ordering is correct regardless of the container's local timezone and
+        # so the Django side doesn't receive a naive datetime.
+        created_at = (
+            datetime.fromtimestamp(item["taken_at"], tz=timezone.utc)
+            if item.get("taken_at")
+            else datetime.now(timezone.utc)
+        )
 
         row = InstagramPost(
             ig_post_id=post_id,