Add edge-case tests for in-memory repositories

[amirHdev]

The in-memory repositories are simple, which is exactly why I want them tested a bit more thoroughly.

There are still some easy edge cases around replace/update behavior and filtered lookups that should be locked down.

Good areas to look at:

• save replacing an existing record
• default-field normalization where that behavior exists
• filtered lookup behavior
• delete/update edge cases
• small persistence-related branches that are currently uncovered

Suggested files:

• internal/adapter/repository/lcp/
• existing repository test files

Acceptance criteria:

• add focused tests for real behavior
• no broad refactor needed
• keep the tests easy to follow
• go test ./... passes

Notes:
This is a good first issue for someone who likes straightforward backend logic and wants something low-risk but still useful.

[roshanir-sudo]

I can help add focused edge-case tests for the in-memory repositories, including replace/update behavior, filtered lookups, and uncovered persistence-related branches.

[amirHdev]

@roshanir-sudo Thanks!