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feat: StarterHub - add window controls (minimize/maximize/close) in top bar, clean aligned design

feat: StarterHub uses real projects_list/project_create/project_load/project_delete backend

fix: StarterHub - remove immature text, show real saved projects, remove shared tab, fix floating panel access

feat: StarterHub - add Recent/Shared tabs, Open File dialog, proper project grid, better transitions

refactor: StarterHub + ContextMenu + Toolbar + LibraryPanel + SettingsPanel + BrowserPanel