Disable "New virtual card" email when activating card grant

[Copilot]

Summary of the problem

Card grant senders receive "New virtual HCB card" emails when recipients activate their grants. This is unintended—the email is meant for users creating their own cards, not for card grant activations.

Describe your changes

StripeCard has an existing skip_notify_user attr_accessor that suppresses the after_create_commit :notify_user callback, but StripeCardService::Create wasn't using it.

• Added skip_notify_user parameter to StripeCardService::Create (defaults to false)
• Set skip_notify_user on the card instance before saving
• Pass skip_notify_user: true from CardGrant#create_stripe_card

# CardGrant#create_stripe_card
self.stripe_card = StripeCardService::Create.new(
  card_type: "virtual",
  event_id:,
  current_user: user,
  ip_address:,
  subledger:,
  skip_notify_user: true,  # Suppress email for card grant activations
).run

Original prompt

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This section details on the original issue you should resolve

<issue_title>[CardGrant] Disable "New virtual card" email when activating card grant</issue_title>
<issue_description>Card grant senders are now getting these emails whenever someone activates their card grant. It wasn't always like this

More context: https://hackclub.slack.com/archives/GBXBFEED9/p1764186679145649</issue_description>

<agent_instructions>Investigate this. See if there's an obvious code change or cause. Then, if you've found one, try and fix it. Otherwise, mention me with your findings and I'll investigate further.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [CardGrant] Disable "New virtual card" email when activating card grant #12255

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[sampoder]

This fix doesn't make sense?