Recover layered architecture restructure

[dorukanil1996]

Summary

• reorganize production code under src/ into Core, Application, Infrastructure, UI, Cloud, and EdgeAgent projects
• recover printer lifecycle, persistence compatibility, credential protection, Cloud/Edge monitoring, and MAUI host fixes
• move and expand unit, integration, and E2E coverage under tests/
• update CI, Docker, solution, tooling, and architecture/recovery documentation for the new layout

Validation

• git diff --check reviewed; remaining whitespace findings are inherited CRLF/trailing-space content in moved legacy files
• secret-pattern scan found only the documented Docker Compose local-development fallback key
• .NET builds/tests could not be rerun on this device because only .NET SDK 9.0.119 is installed and the recovery targets .NET 10
• recovery audit records the prior successful validation: 179 unit tests passed, plus Release builds for Blazor, Cloud, and EdgeAgent
• MAUI was not built because the required workload is unavailable

See docs/RECOVERY_AUDIT.md for provenance, retained work, regressions addressed, and integration decisions.