[Feature Request] Advanced sync filters (exclude/include by Sender, Subject, or Keywords)

[hflocki]

Is your feature request related to a problem?

Currently, the synchronization can only be limited by selecting specific folders/labels. However, many email accounts (like Gmail or standard IMAP) contain automated notifications, spam, or newsletters within the main inbox that users might not want to archive permanently in the PostgreSQL database.

Describe the solution you'd like

It would be amazing to have an "Exclusion / Inclusion Filter Rules" section in the Email Account settings.
Users should be able to define rules based on:

• From / Sender: (e.g., exclude noreply@* or specific addresses)
• Subject: (e.g., exclude emails containing [Alert] or Your daily backup)
• Headers / Keywords

Emails matching these criteria should be skipped during the background synchronization process to keep the archive clean and save database storage.

Describe alternatives you've considered

Sorting emails with provider-side rules (e.g., in Gmail) before they hit the archiver, which requires a lot of manual maintenance on the email server side.

Additional context

This would give users fine-grained control over what actually lands in their long-term archive, especially for high-traffic personal or business inboxes.