Streams refactor + cost categories

Streams Optimization

• Stream save flow optimized: the Query API now returns full_view, eliminating a redundant POST request on save.

Advanced Splits & Filters

• Refactored advanced splits , add helpful tooltips, and improve tag readability.
• Cost category options for advanced splits and filters are now retrieved dynamically.
• Advanced filter selections are now normalized.

UI & Visualization Fixes

• Resolved dropdown z-index issues so menus no longer render behind other elements.
• Expanded chart color palette from 5 to 10 colors, reducing repetition in Visibility Compare.

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