feat(eims): derive buyer City/Country from company profile, not global config

City: EimsMapperContext.buyerCity was declared but never wired anywhere —
always null, silently, for every buyer. No dedicated city column on Company;
derives from Zone via a new EIMS_BUYER_CITY_CODES map, same lookup mechanism
as Region/Wereda but optional (an unmapped zone resolves to null rather than
throwing) — MoR has already accepted a live filing with City null.

Country: previously a single flat EIMS_BUYER_COUNTRY_CODE applied to every
buyer regardless of Company.country. Now reads company.country, resolved via
a new EIMS_BUYER_COUNTRY_CODES name-to-code map; the flat env var becomes a
domestic-only fallback (applies only when country is empty/Ethiopia), so an
unmapped foreign buyer fails locally instead of silently filing as Ethiopia.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/edr-freight-api/src/modules/billing/eims-invoice.mapper.spec.ts

@@ -60,8 +60,11 @@ const context = (over: Partial<EimsMapperContext> = {}): EimsMapperContext => ({
   unitDefault: "PCS",
   incomeWithholdValue: 0,
   transactionWithholdValue: 0,
+  buyerCountryCode: "231", // test-only, not a confirmed real MoR code
+  buyerCountryCodes: {},
   buyerRegionCodes: { "Addis Ababa": "13" },
   buyerWeredaCodes: {},
+  buyerCityCodes: {},
   ...over,
 });
 
@@ -92,6 +95,9 @@ describe("toEimsInvoice", () => {
 
     expect(doc.BuyerDetails).toEqual({
       City: null,
+      // company.country is "Ethiopia" (the domestic default) — resolves to context's flat
+      // buyerCountryCode fallback, not null, per resolveCountryCode.
+      Country: "231",
       Email: "buyer@abc.et",
       HouseNumber: "NEW",
       IdNumber: null,
@@ -100,7 +106,6 @@ describe("toEimsInvoice", () => {
       LegalName: "ABC Trading PLC",
       Phone: "0912345678",
       Region: "13",
-      Country: null,
       Zone: "SHA",
       Kebele: "03",
       VatNumber: "123475885858",
@@ -335,6 +340,52 @@ describe("toEimsInvoice — MoR field constraints", () => {
     ).toThrow(/buyer Wereda "Yeka".*EIMS_BUYER_WEREDA_CODES/);
   });
 
+  it("derives City from the buyer's zone via the city code map", () => {
+    const doc = toEimsInvoice(
+      invoice({ company: { ...invoice().company!, zone: "Kirkos" } }),
+      seller,
+      context({ buyerCityCodes: { Kirkos: "101" } }),
+    );
+    expect(doc.BuyerDetails.City).toBe("101");
+  });
+
+  it("leaves City null (not a throw) when the buyer's zone has no city mapping — City is optional", () => {
+    const doc = toEimsInvoice(
+      invoice({ company: { ...invoice().company!, zone: "Somewhere Else" } }),
+      seller,
+      context({ buyerCityCodes: {} }),
+    );
+    expect(doc.BuyerDetails.City).toBeNull();
+  });
+
+  it("maps a buyer country name to its code via the country code map", () => {
+    const doc = toEimsInvoice(
+      invoice({ company: { ...invoice().company!, country: "Djibouti" } }),
+      seller,
+      context({ buyerCountryCodes: { Djibouti: "071" } }),
+    );
+    expect(doc.BuyerDetails.Country).toBe("071");
+  });
+
+  it("falls back to the flat domestic country code only for Ethiopia, not any unmapped country", () => {
+    const doc = toEimsInvoice(
+      invoice({ company: { ...invoice().company!, country: "Ethiopia" } }),
+      seller,
+      context({ buyerCountryCode: "231", buyerCountryCodes: {} }),
+    );
+    expect(doc.BuyerDetails.Country).toBe("231");
+  });
+
+  it("refuses a genuinely foreign buyer country with no mapping — never silently files it as Ethiopia", () => {
+    expect(() =>
+      toEimsInvoice(
+        invoice({ company: { ...invoice().company!, country: "Kenya" } }),
+        seller,
+        context({ buyerCountryCode: "231", buyerCountryCodes: {} }),
+      ),
+    ).toThrow(/buyer Country "Kenya".*EIMS_BUYER_COUNTRY_CODES/);
+  });
+
   it("emits NatureOfSupplies lowercase, whatever case it was configured in", () => {
     const doc = toEimsInvoice(invoice(), seller, context({ natureOfSupplies: "Service" }));
     expect(doc.ItemList[0].NatureOfSupplies).toBe("service");