[Antreesy]

Fix following case:

• admin sets never, batch_time = 0
• user doesn't touch the setting, batch_time = 5 -> default to user
• lib/MailNotifications.php#sendEmails() sets $batch_time = 0
• next_send_time is updated to previous value + 0, instead of 0 (never send)

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI (ClaudeCode:claude-opus-5-5)

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 9653 was 9158 (+5.4%)
Please check your code again. If you added a new test this can be expected and the base value in tests/Integration/base-query-count.txt can be increased.

[nickvergessen]

/backport to stable35

[nickvergessen]

/backport to stable34

[nickvergessen]

/backport to stable33

[backportbot]

The backport to stable33 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable33
git pull origin stable33

# Create the new backport branch
git checkout -b backport/3575/stable33

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick f543cb7a

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/3575/stable33

Error: Failed to check for changes with origin/stable33: No changes found in backport branch

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.