Default notification email feature flags to off

[aapeliv]

PR #8783 migrated ENABLE_NOTIFICATION_TRANSLATIONS and ENABLE_EMAIL_ICS_ATTACHMENTS from env config to GrowthBook feature flags, but evaluated both with default=True. That leaves both features ON whenever the flag is absent from GrowthBook (or experimentation is disabled), whereas every other feature gate in the codebase (sms_enabled, donations_enabled, strong_verification_enabled, postal_verification_enabled, recaptcha_enabled) defaults to False. This flips notification_translations_enabled and email_ics_attachments_enabled to default=False so the features are off unless explicitly enabled.

Testing

• uv run pytest src/tests/test_calendar_events.py passes (4/4). The existing attachment test still produces attachments because normal tests run with EXPERIMENTATION_PASS_ALL_GATES=True, and the new disabled-test forces the flag off explicitly.

Backend checklist

• Added tests for any new code or added a regression test if fixing a bug
• Run the backend locally and it works
• Added migrations if there are any database changes, rebased onto develop if necessary for linear migration history

For maintainers

• Maintainers can push commits to my branch
• Maintainers can merge this PR for me

This PR was created with the Couchers PR skill.

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Project	Deployment	Actions	Updated (UTC)
couchers	Building	Preview	May 24, 2026 5:46pm

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📝 Release Notes

This PR does not need to be included in release notes.

Reason: This is a small internal configuration fix for notification email feature flags. It does not introduce a new user-facing feature, noticeable UX change, or major infrastructure improvement that end users would care about in release notes.

🤖 Bot Debug Information

Model: couchers.openai.gpt-5.4
Decision: exclude
Reasoning: This is a small internal configuration fix for notification email feature flags. It does not introduce a new user-facing feature, noticeable UX change, or major infrastructure improvement that end users would care about in release notes.