Add time filter persistence, text inputs, and overlay settings panel

[mattdawkins]

Summary

• Persist time filters per dataset in metadata (following the confidenceFilters pattern) so filter state is restored when reopening a dataset
• Add frame number and HH:MM:SS text input fields alongside sliders in the time filter settings panel
• Replace the hover-based popup menu with a click-toggled overlay panel positioned above the controls bar on the right ~1/3 of the screen
• Save time filter changes from the timeline drag handles as well

Test plan

• Open a video dataset, enable a time filter range, navigate away, return — filter should be restored
• Verify text fields accept frame numbers and update the sliders
• Verify time fields (for videos) accept HH:MM:SS and convert correctly
• Verify clicking the filter button enables + opens settings, clicking again disables, clicking outside closes without disabling
• Verify clearing the time filter (toggling off) saves null and is remembered

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