⚡ Bolt: Remove intermediate vector allocations in TUI render loop

[julesklord]

💡 What: Refactored the TUI rendering loop in src/ui.rs to construct ListItems directly from the application state iterators (app.themes, app.fonts, app.segments) rather than allocating intermediate vectors by calling app.filtered_* methods. Removed the now-unused filtered_fonts and filtered_segments methods in src/app/services.rs and updated tests.
🎯 Why: Calling .collect() into intermediate collections merely to iterate over them and map them to UI items creates unnecessary Vec allocations, leading to increased memory pressure and garbage collection overhead during Ratatui's high-frequency render loops.
📊 Impact: Eliminates O(N) heap allocations and deep cloning of structs during each frame render for the fonts and segments views.
🔬 Measurement: Verify changes compile correctly via cargo check and execute without failure via cargo test and npx playwright test. Observe reduced CPU and memory footprint during continuous TUI list filtering.

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PR created automatically by Jules for task 17225690199213653854 started by @julesklord

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