l10n: improve Swedish security and connection UI

[yeager]

Summary

• update Swedish authentication, private-key password, proxy, certificate and QR authentication dialogs
• translate connection settings, failure states, route errors and core tray actions
• add three resource IDs that were absent from Swedish

Validation

• Swedish and English resource ID sets now match
• git diff --check passes

This is a focused improvement to the existing Swedish resource; it deliberately leaves unrelated legacy wording for a subsequent review.