feat: MercadoLibre integration + inventory bulk publish + WhatsApp bridge fixes

- Add MercadoLibre OAuth, listings, orders, webhooks and category search
- New marketplace_external_bp.py, meli_service.py, marketplace_external_service.py
- New marketplace_external.html/js with ML management UI
- Inventory: bulk publish to ML with category autocomplete, listing type and shipping selectors
- Inventory: new .btn--meli styles, select/label CSS fixes
- WhatsApp bridge: rate limiting, 440/515/408 error handling, stale watchdog
- DB migration v3.4_meli_integration.sql for marketplace_listings, orders, sync_queue
- Add Celery tasks for ML sync and webhook processing
- Sidebar: MercadoLibre navigation link

pos/tasks.py

@@ -98,6 +98,133 @@ def generate_report_task(self, report_type, params, tenant_id):
     }
 
 
+# ─── MercadoLibre Tasks ───────────────────────────────────────────────────
+
+@celery.task(bind=True, max_retries=3)
+def sync_meli_stock_price_task(self, tenant_id: int):
+    """Sync stock and price for all active ML listings."""
+    from services import marketplace_external_service as meli_svc
+    from tenant_db import get_tenant_conn
+
+    conn = get_tenant_conn(tenant_id)
+    try:
+        cfg = meli_svc.get_meli_config(conn)
+        svc = meli_svc._get_meli_service(cfg)
+        if not svc:
+            return {'error': 'MercadoLibre not configured'}
+
+        cur = conn.cursor()
+        cur.execute(
+            """
+            SELECT id, inventory_id, external_item_id, publish_price
+            FROM marketplace_listings
+            WHERE is_active = true AND channel = 'mercadolibre'
+            """
+        )
+        listings = cur.fetchall()
+        cur.close()
+
+        from services.inventory_engine import get_stock_bulk
+        stock_map = get_stock_bulk(conn, branch_id=None)
+
+        updated = 0
+        failed = 0
+        for row in listings:
+            listing_id, inv_id, ext_id, last_price = row
+            cur = conn.cursor()
+            cur.execute("SELECT price_1 FROM inventory WHERE id = %s", (inv_id,))
+            price_row = cur.fetchone()
+            cur.close()
+            current_price = float(price_row[0]) if price_row and price_row[0] else 0
+            current_stock = stock_map.get(inv_id, 0)
+
+            try:
+                svc.update_item(
+                    ext_id,
+                    {"price": round(current_price, 2), "available_quantity": max(current_stock, 0)},
+                )
+                cur = conn.cursor()
+                cur.execute(
+                    """
+                    UPDATE marketplace_listings
+                    SET last_sync_at = NOW(), sync_errors = NULL, publish_price = %s
+                    WHERE id = %s
+                    """,
+                    (current_price, listing_id),
+                )
+                conn.commit()
+                cur.close()
+                updated += 1
+            except Exception as e:
+                conn.rollback()
+                cur = conn.cursor()
+                cur.execute(
+                    "UPDATE marketplace_listings SET sync_errors = %s WHERE id = %s",
+                    (str(e)[:500], listing_id),
+                )
+                conn.commit()
+                cur.close()
+                failed += 1
+
+        return {'updated': updated, 'failed': failed, 'total': len(listings)}
+    finally:
+        conn.close()
+
+
+@celery.task(bind=True, max_retries=3)
+def sync_meli_orders_task(self, tenant_id: int):
+    """Fetch new orders from MercadoLibre."""
+    from services import marketplace_external_service as meli_svc
+    from tenant_db import get_tenant_conn
+
+    conn = get_tenant_conn(tenant_id)
+    try:
+        # Determine last check date from most recent order
+        cur = conn.cursor()
+        cur.execute(
+            "SELECT MAX(created_at) FROM marketplace_orders WHERE channel = 'mercadolibre'"
+        )
+        row = cur.fetchone()
+        last_check = row[0]
+        cur.close()
+
+        date_from = None
+        if last_check:
+            date_from = last_check.strftime('%Y-%m-%dT%H:%M:%S.000-00:00')
+
+        result = meli_svc.fetch_and_save_orders(conn, date_from=date_from)
+        return result
+    except Exception as e:
+        return {'error': str(e)}
+    finally:
+        conn.close()
+
+
+@celery.task(bind=True, max_retries=3)
+def process_meli_webhook_task(self, tenant_id: int, topic: str, resource: str):
+    """Process incoming MercadoLibre webhook asynchronously."""
+    from services import marketplace_external_service as meli_svc
+    from tenant_db import get_tenant_conn
+
+    conn = get_tenant_conn(tenant_id)
+    try:
+        if topic.startswith("orders"):
+            # Fetch full order and upsert
+            cfg = meli_svc.get_meli_config(conn)
+            svc = meli_svc._get_meli_service(cfg)
+            if svc and resource:
+                order_id = resource.split("/")[-1]
+                full = svc.get_order(order_id)
+                # Re-use fetch_and_save_orders by passing the order directly
+                # For simplicity, trigger a full sync for recent orders
+                return meli_svc.fetch_and_save_orders(conn)
+        return {'ok': True, 'topic': topic}
+    except Exception as e:
+        return {'error': str(e)}
+    finally:
+        conn.close()
+
+
 @celery.task(bind=True, max_retries=2)
 def sync_vehicle_compatibility_task(self, tenant_id, item_id, part_number, name, brand, compat_source):
     """Fetch AI/TecDoc vehicle compatibility in background after item creation."""