chore: remove superseded root projects — Shared, Blazor, MAUI, Tests migrated to src/

All content from MakerPrompt.Shared, MakerPrompt.Blazor, MakerPrompt.MAUI, and
MakerPrompt.Tests has been fully migrated to the src/ clean-architecture projects:
  - MakerPrompt.Shared → src/MakerPrompt.Core + src/MakerPrompt.UI.Components
  - MakerPrompt.Blazor → src/MakerPrompt.UI.Blazor
  - MakerPrompt.MAUI  → src/MakerPrompt.UI.MAUI
  - MakerPrompt.Tests → src/MakerPrompt.Tests.Unit (185 tests passing)

MakerPrompt.E2E.Maui and MakerPrompt.E2E.Wasm are retained (not yet ported).
MakerPrompt.Shared.ShapeIt removed (empty stub, not in solution).

Author: akinbender