Refactor DataLocationResolver to centralize data path resolution (ResolveLauncherDataPath, ResolveDesktopDataPath, ResolveConfigPath, ResolveLauncherLogsPath, ResolveLauncherStatePath) and replace usages of the previous ".launcher" layout with a "Launcher" folder. Update API: LoadConfig/SaveConfig reorganized and ApplyLocationChoice now accepts an optional custom path and migration flag; migration logic updated accordingly. Update dependent services and views (Logger, DeploymentLocator, UpdateEngineService, OobeStateService, StartupAttemptRegistry, LauncherDebugSettingsStore, OobeWindow) to use the new resolver APIs and paths. Add LauncherBackgroundService to load/validate/cache a custom splash background image and wire it into SplashWindow (AXAML/Axaml.cs) with UI placeholders and overlay. Misc: minor cleanup of Oobe/Splash XAML and related code adjustments and logging improvements.
Introduce a redesigned OOBE flow and data-location/theme support across the launcher. Adds a new ThemeService for applying light/dark and accent colors; integrates FluentIcons.Avalonia package for icons. Overhauls OobeWindow (UX animations, typing effect, multi-step theme and data-location pages, Monet options, and final welcome step) and its code-behind to handle step navigation, accent selection, and data-location resolution. Adds DataLocation UI and handlers (DataLocationPromptWindow changes, DataLocation resolver usage) and wires a DevDebug UI for toggling/opening the data-location page. UpdateEngineService now resolves the launcher root via DataLocationResolver. Misc: update various view models, localization entries and remove TrimmerRoots.xml.
