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.
Introduce support for choosing and resolving the application's data root (system user dir vs. portable app folder). Adds DataLocationConfig model, DataLocationResolver (load/save/resolve/migrate), a UI prompt (DataLocationPromptWindow) and an OOBE step (DataLocationOobeStep) to let users pick and optionally migrate existing data. Wire the chosen data root into the launcher flow and host launch plan (forwarded via --data-root and LMD_DATA_ROOT), and add AppDataPathProvider to let runtime services read the effective data root (initialized in Program.Main). Update various services (logging, settings, DB, plugin/market, startup registry, etc.) to use the new provider/resolver and register the config type in the JSON context. This enables portable installs, safe migration, and runtime overrides via CLI or environment variable.
