[PM-43240] fix: preserve custom authenticator refresh periods when editing

[mvanhorn]

🎟️ Tracking

Change EditItemData.refreshPeriod to hold integer seconds, and retain the initially loaded period separately in that same Parcelable model so the picker can still offer it after the user temporarily selects a preset. In EditItemViewModel, initialize both values from the entity's actual period, remove the fromSeconds(...) ?: THIRTY conversion, carry integer seconds through RefreshPeriodOptionClick and its handler, and save the selected value directly to AuthenticatorItemEntity.period. In EditItemScreen, update the callbacks and previews and build the picker from the existing preset seconds plus the original custom period, deduplicated and sorted, using the existing refresh_period_seconds plural resource for both labels and the selected value.

Authenticator 2026.8.0 can scan a working TOTP entry with a 45-second refresh period, but saving an edit to its name or username changes the period to 30 seconds and breaks the generated codes. The September 3 reporter follow-up confirms that the failure occurs after an ordinary metadata edit, making the data-loss behavior concrete despite the feature-oriented issue title. The maintainer initially redirected custom period entry to the feature forum, then reopened the issue for investigation after the bug was clarified. This plan addresses that confirmed defect and displays the imported custom period as a selectable value; a general-purpose manual period editor remains outside this contribution.

Fixes #7347

📔 Objective

Not applicable to this change.

📸 Screenshots

No user-visible surface changes in this PR, so there is nothing to show.

[bitwarden-bot]

Thank you for your contribution! We've added this to our internal tracking system for review.
ID: PM-43240
Link: https://bitwarden.atlassian.net/browse/PM-43240

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