fix(project): Use an annotated type for duration strings

[lengau]

Inspired by: #5210

This makes an annotated type for duration strings and uses a stricter regex.

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[lengau]

Surprisingly, just an integer isn't a valid duration. The current snapcraft will error out during the packing step:

$ snapcraft_edge pack
Generated snap metadata
Cannot pack snap: error: cannot parse snap.yaml: time: missing unit in duration "10"
Detailed information: Command '['snap', 'pack', '--check-skeleton', PosixPath('/root/prime')]' returned non-zero exit status 1.
Failed to execute pack in instance.
Recommended resolution: Run the same command again with --debug to shell into the environment if you wish to introspect this failure.
Full execution log: '/home/lengau/.local/state/snapcraft/log/snapcraft-20250121-181707.415584.log'

[lengau]

I added a separate data entry for a valid duration here, as "10m4s3us" is a valid duration string. Snapd uses time.ParseDuration to parse this, and the resulting service file contains a value something like TimeoutStartSec=604.000003.

[mr-cal]

Thank you!

Do you mind targeting hotfix/8.6? The hotfix/8.5 branch is closing in favor of 8.6 this week and I can get this into 8.6.0 or 8.6.1, depending on the timing. It may require a touch of rebasing as Sergio updated the project model.

[lengau]

@mr-cal done! I'll take this out of draft once I ensure CI is still succeeding, and then since it was his fine work that gave me a conflict during rebase I'll ask @sergiusens to review.