BUG: Handle invalid filters consistently

[nourinmohd]

Resolves #282

• Added validation in LogManager.filter_log() so unknown fields and incompatible FilterType/field combinations raise ValueError before Pandas filtering.
• Short-circuited empty logs to return an empty log of the same model type.
• Added regression tests for empty logs, unknown fields, and invalid text/date/number filter combinations.

Checklist

• Tests added (if not, comment why)
• Test coverage equal or up from main (run pytest with --cov=src/ --cov-report term-missing)
• If not squash merging, every commit passes tests
• Appropriate commit prefix and precise commit message used
• All debug prints and unnecessary comments removed
• Docstrings are correct and updated
• Documentation is updated, if necessary
• Latest main rebased/merged into branch
• Added comments on this PR where appropriate to help reviewers
• Moved issue status on project board
• Checked the boxes in this checklist ✅

[GibranAlfa]

nice work 👍