fix(payments-next): Add free trial reactivation email variant

[david1alvarez]

Because:

• Upon reactivating a free trial after cancelling it, the user receives an email. This email contains language centered around full subscriptions

This commit:

• Updates the emails to include a conditional, changing the banner to reference renewing the users trial when a free trial is being renewed

Closes #PAY-3656

Checklist

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• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).
• I have manually reviewed all AI generated code.

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(free trial variant)

(subscription variant, current/unchanged)

[Copilot]

Pull request overview

Adds a free-trial-specific title variant for the “subscription reactivation” transactional email so users reactivating during an active free trial don’t see subscription-centric banner language.

Changes:

• Introduces isFreeTrialReactivation and uses it to conditionally select a “trial reactivated” title in the subscriptionReactivation templates (MJML + plaintext) with new FTL string.
• Threads isFreeTrialReactivation from Stripe subscription status → auth-server mailer template values.
• Bumps template version(s) and updates Storybook stories; adjusts Stripe reactivation-details test expectations.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/fxa-auth-server/lib/senders/emails/templates/subscriptionReactivation/index.txt	Conditional plaintext title key for free-trial vs subscription reactivation.
packages/fxa-auth-server/lib/senders/emails/templates/subscriptionReactivation/index.mjml	Conditional banner/title rendering based on isFreeTrialReactivation.
packages/fxa-auth-server/lib/senders/emails/templates/subscriptionReactivation/en.ftl	Adds subscriptionReactivation-freeTrial-title localization string.
packages/fxa-auth-server/lib/senders/emails/templates/subscriptionReactivation/index.stories.ts	Adds Storybook story variant exercising the free-trial title.
packages/fxa-auth-server/lib/senders/emails/templates/_versions.json	Bumps subscriptionReactivation template version to 3.
packages/fxa-auth-server/lib/senders/email.js	Passes isFreeTrialReactivation into template values (default false).
packages/fxa-auth-server/lib/payments/stripe.ts	Sets isFreeTrialReactivation based on Stripe subscription status.
packages/fxa-auth-server/lib/payments/stripe.spec.ts	Updates expected reactivation-details payload to include isFreeTrialReactivation.
libs/accounts/email-renderer/src/templates/subscriptionReactivation/index.txt	Mirrors conditional plaintext title key for free-trial vs subscription reactivation.
libs/accounts/email-renderer/src/templates/subscriptionReactivation/index.mjml	Mirrors conditional banner/title rendering based on isFreeTrialReactivation.
libs/accounts/email-renderer/src/templates/subscriptionReactivation/en.ftl	Mirrors new free-trial title localization string.
libs/accounts/email-renderer/src/templates/subscriptionReactivation/index.stories.ts	Adds renderer Storybook variant for free-trial reactivation.
libs/accounts/email-renderer/src/templates/subscriptionReactivation/index.ts	Adds isFreeTrialReactivation to template data and bumps template version to 3.

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[Copilot]

isFreeTrialReactivation is derived from subscription.status === 'trialing', but the existing tests for extractSubscriptionUpdateReactivationDetailsForEmail only cover the active status (and now assert false). Please add a test case that sets the fixture subscription status to trialing (or uses a trialing fixture) and asserts isFreeTrialReactivation: true to prevent regressions in the free-trial email variant path.