[Application Builder] Unify configuration, settings, logging, and desktop services

[KlausLoeffelmann]

User story

As a WinForms developer, I want modern configuration, options, user settings, logging, exception handling, and background/health services through one extensible model so that desktop applications use familiar .NET infrastructure without losing desktop-specific behavior.

Rationale and user benefit

The builder should make common infrastructure consistent with other .NET workloads while respecting per-user settings, UI-thread dispatch, application lifetime, offline desktop operation, privacy, and deployment constraints.

Scope boundary

Own configuration/options integration, the modern settings abstraction and migration path, logging providers/extensions, exception services, hosted/background services, and appropriate health diagnostics. Consume host/lifetime and DI contracts; do not own their implementation or templates.

Acceptance criteria

• Configuration sources and precedence are documented and predictable.
• Strongly typed options and validation work before UI startup.
• Per-user settings can load, save, upgrade, and report failures without silently losing data.
• Logging and exception handling preserve UI-thread context and do not expose sensitive data by default.
• Background and health services stop cleanly with the application.
• Third parties can extend the builder without internal dependencies.

Definition of Done

• Service boundaries and defaults are API-reviewed.
• Implementations, tests, samples, migration guidance, and diagnostics are complete.
• File contention, corruption, cancellation, privacy, deployment, performance, and resource stability are validated.

Parallelization

This is foundation stream C. Work behind extension methods and service contracts so streams A and B do not need to edit these providers.