feat(schema): learn sender-specific mappings

[xt0n1-t3ch]

Summary

Closes #34.

Implements hybrid auto schema mapping for sender-specific bordereaux: static canonical aliases for cold start, learned EF overrides keyed by sender/domain after analyst correction, visible mapping evidence in Review, and normalized mapped values.

What changed

• Added schemaMappings to document details plus mapping corrections on review decisions.
• Added EF persistence for per-document mapping evidence and learned sender/domain mapping rules.
• Added a scoped schema mapper with precedence: learned override -> static alias -> bounded fuzzy match -> low-confidence unmapped row.
• Applied mapped table values into canonical fields when extraction is missing/low-confidence, with normalization for money, percent, currency, dates, and simple codes.
• Added Review UI Schema mapping panel with source header, canonical target, confidence/source, normalized value, sender key, and correction staging.
• Updated extraction contract, docs, and test index.

Testing

• dotnet build Reva.slnx -warnaserror -> passed, 0 warnings.
• dotnet format Reva.slnx --verify-no-changes -> passed.
• dotnet test Reva.slnx -> passed, 28 unit + 14 integration.
• dotnet build tests/Reva.E2E/Reva.E2E.csproj -> passed, 0 warnings.
• pwsh tests/Reva.E2E/bin/Debug/net10.0/playwright.ps1 install chromium -> passed.
• dotnet test tests/Reva.E2E/Reva.E2E.csproj --no-build -> passed, 3 e2e.
• Browser proof at http://localhost:5187: uploaded a sender .eml, verified Schema mapping panel, corrected GWP -> Claims, saved, saw Corrected 99% + Claims marked Reviewed, console errors [].