feat(maui): add font size setting to MAUI app (fixes #165)

[fboucher]

Resolves #165 by adding a font size setting to the MAUI app.

Summary of Changes

• Domain & Local Storage: Added FontSize string property to Settings domain model and LocalSettings SQLite model with mapping between domain and local database.
• Settings UI: Added a Font Size dropdown (FluentSelect) to Settings.razor allowing users to select Small, Medium, or Large.
• CSS Custom Property: Defined --app-font-size and bound it to html, body and FluentUI typography custom properties in MAUI app's �pp.css.
• Dynamic Application: Restored saved font size on app load in MainLayout.razor and updated --app-font-size dynamically via JS Interop upon save.
• Unit Tests: Added tests in SettingsTests.cs, LocalDataServiceTests.cs, and FontSizeHelperTests.cs.

[github-actions]

Package	Line Rate	Branch Rate	Health
NoteBookmark.AIServices	97%	64%	✔
NoteBookmark.Api	89%	79%	✔
NoteBookmark.BlazorApp	5%	10%	❌
NoteBookmark.Domain	86%	75%	✔
NoteBookmark.ServiceDefaults	96%	75%	✔
NoteBookmark.SharedUI	15%	20%	❌
Summary	53% (925 / 1740)	44% (238 / 541)	❌