fix: Sort by "last modified" (issue #5158)

[v3DJG6GL]

Summary

Fix #5158

With sort order set to Last modified:

• Switching between groups (e.g. All contacts ↔ Not grouped) showed an error:

  Unable to retrieve the contact from the server, please check your network connection.
  

• After reloading the page, the sort setting was reset to the previous value.
• This issue was described in Bug: Sort by "last modified" is not working #5158

Underlying issue: sorting crashed whenever any contact had a missing or malformed REV (last-modified) value:
The code called a date method on every contact's REV. If REV was missing or not a valid date, it threw an error.

Changes

• Read each contact's REV once when contacts are first loaded from the server, and store a plain timestamp (or null if it's missing/unreadable).
• Contacts with no valid REV sort to the end instead of crashing the list.
• Tolerate malformed date strings (e.g. wrong format, missing seconds) by parsing them defensively.
• Make the rev getter return null on error instead of throwing, so one contact with a broken REV can't crash the component that reads it.
• Stop fabricating REV = now when one is missing (both in the Contact constructor and in a background auto-"fix"). The old behavior made contacts jump to the top every time they were touched.
• Don't re-sort the whole list when a contact is opened. Its stored REV doesn't change just because it was viewed.
• Replaced custom scroll math with the list library's built-in scroll-into-view, which prevents visible jumps when the list updates.

LLM Disclosure

Developed with assistance from Claude Code (Opus 4.7, 1M context).
The LLM helped me identify the related files, code parts and proposed possible code modifications and fixes.
I've manually reviewed, the code the best I could.
A proper code review is required in any case...

[codecov]

Codecov Report

❌ Patch coverage is 0% with 57 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/store/contacts.js	0.00%	23 Missing and 12 partials ⚠️
src/models/contact.js	0.00%	16 Missing and 6 partials ⚠️

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