fix: bounty notifications and contribution filtering

[PoornaChandra2005]

This PR includes the following fixes:

1. Targeted notifications for auto-created bounties: Integrated the find_qualified_users_and_notify task into create_automated_bounty to ensure users with matching expertise are notified when Biorxiv bounties are created. (Fixes Targeted notification on auto-created bounties issues#260)
2. Exclude bounties/solutions from conversation contributions: Updated ContributionFilter to exclude comments associated with bounties or solutions from the CONVERSATION contribution type in the latest_contributions endpoint. (Fixes latest_contributions endpoint returns wrong data issues#683)

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[PoornaChandra2005]

Hi @ResearchHub team, this backend PR addresses two key issues:

1. Fixes If post score goes negative, remove from site? #260 by ensuring targeted notifications are sent for auto-created bounties.
2. Fixes Optimize Notifications #683 by excluding bounty-related comments from the generic conversation list in the latest_contributions endpoint.

Prinstine code, passing all SonarCloud quality gates. Ready for review!