Fix retention time filtering for missing metadata

[janusson]

Fixes an issue where SimilarityEngine would crash with ValueError when encountering non-numeric retention time metadata (like "None" or "NaN") during the rt_tolerance check. The retention time values are now safely parsed using a try...except block for ValueError and TypeError, and missing metadata is properly ignored without crashing the engine.

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PR created automatically by Jules for task 17231161644105973632 started by @janusson

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[janusson]

@jules I have made significant changes to the codebase since this PR was opened. Please re-evaluate your implementation based on the current state of the main branch and update the code to ensure it still fits the current architecture.

[google-labs-jules]

@jules I have made significant changes to the codebase since this PR was opened. Please re-evaluate your implementation based on the current state of the main branch and update the code to ensure it still fits the current architecture.

I have successfully rebased the branch to the current state of the main branch and confirmed that the tests pass. The codebase update to main already includes rt_tolerance in SimilarityConfig, so only the logic for handling missing and invalid retention time values in similarity.py and its corresponding test in tests/test_v1_1_features.py were required.