feat(rates): last-mile rate rules with bulk per-ton-km and container distance bands

- rates: min_km/max_km columns, PER_TON_KM unit, ETB|USD currency for last mile
- extend UQ_rates_pattern with band start; overlap + shape validation
- shared last-mile charge resolver; approve-dialog price estimate endpoint
- delivery-fee invoice prices via rules, falls back to vehicle price/km
- backoffice: last-mile rate form (mode, container type, band, currency)

apps/edr-freight-web/backoffice/src/pages/ruleEngine/RuleEngineResourcePage.tsx

@@ -584,10 +584,30 @@ const RuleEngineResourcePage = () => {
       // treats them as ALWAYS. Surcharges (Applies to = Other) keep their
       // chosen trigger.
       const isSurcharge = values.appliesTo === "OTHER";
+      // Last mile: the form's calculation mode picks the unit (bulk = per
+      // ton·km, container = per km + distance band) and the currency stays as
+      // chosen (birr or dollar). Everything else remains USD-only.
+      const isLastMile = values.appliesTo === "LAST_MILE";
+      const { lastMileMode, ...rest } = values;
       payload = {
-        ...values,
-        currency: "USD",
+        ...rest,
+        currency: isLastMile ? (values.currency ?? "ETB") : "USD",
         trigger: isSurcharge ? values.trigger : "ALWAYS",
+        ...(isLastMile
+          ? lastMileMode === "BULK"
+            ? {
+                rateUnit: "PER_TON_KM",
+                containerTypeId: undefined,
+                minKm: undefined,
+                maxKm: undefined,
+              }
+            : {
+                rateUnit: "PER_KM",
+                // Empty "To km" means an open-ended band — send null so an
+                // edit can clear a previously-set ceiling.
+                maxKm: values.maxKm ?? null,
+              }
+          : {}),
       };
       // Editing a LIVE rate files a change request — the rate keeps charging
       // its current value until an approver applies it. DRAFT rates fall