Refactor configuration management to use SQLite and add Blazor components

[JeffrySteegmans]

This pull request introduces significant architectural changes to the SendHub application, focusing on removing the old Daemon-based backend and replacing it with a new web-based backend. The configuration and application settings are now managed via a SQLite-backed settings provider, and the SMTP/email sending logic has been refactored to use this new provider. Additionally, conventions for Blazor component development have been documented. Below are the most important changes grouped by theme:

Backend Architecture Changes:

• Removed the Daemon backend (SendHub.Daemon), its configuration, and tests, and replaced it with a new web-based backend (SendHub.Web) in the solution and application host. The app host and project references now point to SendHub.Web instead of the Daemon. (SendHub.slnx, AppHost.cs, SendHub.AppHost.csproj, FolderWatcherSettings.cs, appsettings.json) [1] [2] [3] [4] [5]

Configuration and Settings Refactor:

• Introduced a new SqliteApplicationSettings class implementing IApplicationSettings, which persists all application settings (including SMTP and folder paths) in a SQLite database table. This class provides methods for reading, updating, and seeding default settings. (SqliteApplicationSettings.cs)
• Updated dependency injection to register SqliteApplicationSettings as the singleton settings provider and removed the previous options-based configuration for SMTP and folder watcher settings. (Registration.cs)

Email/SMTP Logic Refactor:

• Refactored SmtpFileSender to use the new IApplicationSettings interface for all configuration, removing the SmtpSettings options class and associated validation. (SmtpFileSender.cs, SmtpSettings.cs) [1] [2]
• Updated and simplified related tests to use the new settings provider and removed validation-specific tests. (SmtpFileSenderTests.cs)

Testing and Infrastructure:

• Added comprehensive tests for SqliteApplicationSettings to verify initialization, default seeding, updates, and idempotency. (SqliteApplicationSettingsTests.cs)
• Moved test fakes to align with the new backend structure. (FakeFileSystemWatcher.cs)

Development Conventions:

• Documented Blazor code-behind conventions, enforcing separation of markup and logic, and proper use of dependency injection in .razor.cs files. (claude.md)

Additional:

• Added MudBlazor UI library to dependencies for future UI work. (Directory.Packages.props)