Use metric by default

frontend/src/contexts/DistanceUnitContext.tsx

@@ -10,7 +10,7 @@ interface DistanceUnitContextValue {
 const noop = () => {};
 
 const DistanceUnitContext = createContext<DistanceUnitContextValue>({
-  distanceUnit: 'imperial',
+  distanceUnit: 'metric',
   setDistanceUnit: noop,
 });
 

frontend/src/test/distanceUnits.test.ts

@@ -11,8 +11,8 @@ describe('distanceUnits utilities', () => {
     localStorage.clear();
   });
 
-  it('defaults to imperial when unset', () => {
-    expect(getSavedDistanceUnit()).toBe('imperial');
+  it('defaults to metric when unset', () => {
+    expect(getSavedDistanceUnit()).toBe('metric');
   });
 
   it('returns the stored unit when valid', () => {
@@ -20,9 +20,9 @@ describe('distanceUnits utilities', () => {
     expect(getSavedDistanceUnit()).toBe('metric');
   });
 
-  it('falls back to imperial for invalid stored values', () => {
+  it('falls back to metric for invalid stored values', () => {
     localStorage.setItem(DISTANCE_UNIT_KEY, 'parsecs');
-    expect(getSavedDistanceUnit()).toBe('imperial');
+    expect(getSavedDistanceUnit()).toBe('metric');
   });
 
   it('stores the selected distance unit', () => {

frontend/src/test/settingsModal.test.tsx

@@ -536,12 +536,12 @@ describe('SettingsModal', () => {
     expect(localStorage.getItem(LAST_VIEWED_CONVERSATION_KEY)).toBeNull();
   });
 
-  it('defaults distance units to imperial and stores local changes', () => {
+  it('defaults distance units to metric and stores local changes', () => {
     renderModal();
     openLocalSection();
 
     const select = screen.getByLabelText('Distance Units');
-    expect(select).toHaveValue('imperial');
+    expect(select).toHaveValue('metric');
 
     fireEvent.change(select, { target: { value: 'smoots' } });
 

frontend/src/utils/distanceUnits.ts

@@ -17,9 +17,9 @@ function isDistanceUnit(value: unknown): value is DistanceUnit {
 export function getSavedDistanceUnit(): DistanceUnit {
   try {
     const raw = localStorage.getItem(DISTANCE_UNIT_KEY);
-    return isDistanceUnit(raw) ? raw : 'imperial';
+    return isDistanceUnit(raw) ? raw : 'metric';
   } catch {
-    return 'imperial';
+    return 'metric';
   }
 }