Audit for database queries that use `firstOrNull` instead of a `limit`

[nullpointer0x00]

Summary

Audit the codebase for database queries returning large datasets and using firstOrNull on the Kotlin side, which can be optimized by adding limit(1) directly in the database query.

Problem Definition

Some queries were fetching and serializing large datasets, up to 316k records, only to use the first result with firstOrNull. This caused longer query times, unnecessary network data transfer, and serialization overhead. See PR #544 for a related example.

Proposal

Perform an audit to identify and update such queries to include limit(1) where appropriate.

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For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged
• Contributor assigned/self-assigned