fix(preferences): normalize stored preference hydration

[snkk2x-collab]

Summary

• normalize stored UI preferences before hydration so partial or legacy records keep nested receipt defaults
• validate enum-like preference fields and fall back to supported defaults for unsupported stored values
• normalize stored layout preferences so invalid widths fall back to defaults and valid widths stay clamped
• add regression coverage for partial UI records, unsupported UI values, and layout width restoration

Fixes #971

Before / After

Before, a partial stored receipts object could replace the default receipt policy object during hydration, and invalid stored layout width values could restore unpredictably. After this change, hydration produces a complete preference record with preserved defaults and bounded layout values.

Validation

• pnpm exec vitest run src/features/preferences/preferences.test.ts
• pnpm exec tsc --noEmit
• pnpm exec eslint src/features/preferences/usePreferences.ts src/features/preferences/useLayoutPreferences.ts src/features/preferences/preferences.test.ts