Make backup file names more user friendly

[emontnemery]

Breaking change

This may be a breaking change in cases where automations rely on backup files being named {backup_id}.tar

Proposed change

Make backup file names more user friendly

Without this PR, backups are named {backup_id}.tar.
The PR proposes to change the naming to {name}_-_{date}_{hh.mm}_{xxxxxxxx}.tar, for example Custom_backup_2025.1.0_-_2025-01-30_05.42_12345678.tar.

Considered alternative naming schemes:

• Colon as time separator: Custom backup 2025.1.0 - 2025-01-30 05:42 12345678.tar. This has been ruled out because colons are forbidden by Windows file systems
• No mangling of the file names: Custom backup 2025.1.0 - 2025-01-30 05.42 12345678.tar. This has been ruled out to allow broken shell scripts which don't quote file names to work.

Note that the last part of the filename, 12345678 in the example, is NOT the same as the backup_id. In this PR, the last part of the filename is seconds + microseconds, but that's subject to change and should not be relied on.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
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• Tests have been added to verify that the new code works.

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• Documentation added/updated for www.home-assistant.io

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To help with the load of incoming pull requests:

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[home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as it has been labeled with an integration (backup) you are listed as a code owner for? Thanks!

Code owner commands

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• @home-assistant close Closes the pull request.
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• @home-assistant reopen Reopen the pull request.
• @home-assistant unassign backup Removes the current integration label and assignees on the pull request, add the integration domain after the command.
• @home-assistant add-label needs-more-information Add a label (needs-more-information, problem in dependency, problem in custom component) to the pull request.
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[hmmbob]

Fixes #136920