fix flaky sqlite test contention

Increase DBConnection queue tolerance to stop requests being dropped
under load, and flip 3 write-heavy test files to async: false since
SQLite's single-writer model doesn't play well with concurrent writes.

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

test/berrypod/media_test.exs

@@ -1,5 +1,5 @@
 defmodule Berrypod.MediaTest do
-  use Berrypod.DataCase, async: true
+  use Berrypod.DataCase, async: false
 
   alias Berrypod.Media
 

test/berrypod/orders/order_notifier_test.exs

@@ -1,5 +1,5 @@
 defmodule Berrypod.Orders.OrderNotifierTest do
-  use Berrypod.DataCase, async: true
+  use Berrypod.DataCase, async: false
 
   import Swoosh.TestAssertions
   import Berrypod.OrdersFixtures

test/berrypod/products/product_test.exs

@@ -1,5 +1,5 @@
 defmodule Berrypod.Products.ProductTest do
-  use Berrypod.DataCase, async: true
+  use Berrypod.DataCase, async: false
 
   alias Berrypod.Products.Product