Fix GetCountry ToLower index skip

[adedw]

What to build

The GetCountryQuery handler compares c.ISO3Code.ToLower().Equals(...), which translates to LOWER() on both sides of the predicate — the index on the char(3) PK is not used. Compare the ISO3 code directly against the PK column (WHERE iso3 = @p) and handle case-insensitivity client-side (PK is char(3); string.Equals(..., StringComparison.OrdinalIgnoreCase) after fetch).

Acceptance criteria

• Generated SQL compares the PK column directly — no LOWER() on the indexed side (verifiable via query plan or logged SQL).
• Country lookup remains case-insensitive from the caller's perspective.
• Build and app smoke pass.

Blocked by

None (can start immediately).