Add "use my current location" button to Journey entry editor

- One-shot getCurrentPositionOnce() helper in useGeolocation with typed
  error codes (unsupported, insecure context, permission denied, timeout)
- Button inside the entry editor Location field fills coordinates from the
  device and reverse-geocodes the place name via /api/maps/reverse,
  falling back to formatted coordinates when no name is available
- New journey.editor.* i18n keys in all 23 locales
- Unit tests for the helper and component tests for the button flow

client/src/hooks/useGeolocation.test.ts

@@ -1,6 +1,6 @@
-// FE-HOOK-GEO-001 to FE-HOOK-GEO-014
+// FE-HOOK-GEO-001 to FE-HOOK-GEO-023
 import { act, renderHook } from '@testing-library/react';
-import { useGeolocation } from './useGeolocation';
+import { GeoOnceError, getCurrentPositionOnce, useGeolocation } from './useGeolocation';
 
 type WatchSuccess = (pos: GeolocationPosition) => void;
 type WatchFailure = (err: GeolocationPositionError) => void;
@@ -259,3 +259,52 @@ describe('useGeolocation', () => {
     expect(clearWatch).toHaveBeenCalledWith(7);
   });
 });
+
+describe('getCurrentPositionOnce', () => {
+  /** Swaps the watch-based stub from beforeEach for a one-shot one. */
+  function stubOnce(getCurrentPosition: (ok: PositionCallback, fail?: PositionErrorCallback) => void): void {
+    Object.defineProperty(navigator, 'geolocation', {
+      value: { getCurrentPosition: vi.fn(getCurrentPosition) },
+      configurable: true,
+    });
+  }
+
+  it('FE-HOOK-GEO-020: resolves a mapped position from a single fix', async () => {
+    stubOnce(ok => ok(fix({ latitude: 41.9, longitude: 12.5, accuracy: 10 })));
+
+    await expect(getCurrentPositionOnce()).resolves.toEqual({
+      lat: 41.9, lng: 12.5, accuracy: 10, heading: null, speed: null, timestamp: 1_700_000_000_000,
+    });
+  });
+
+  it('FE-HOOK-GEO-021: rejects as unsupported when the browser has no geolocation', async () => {
+    // Same guard as FE-HOOK-GEO-008: the key has to go away entirely.
+    delete (navigator as { geolocation?: Geolocation }).geolocation;
+
+    await expect(getCurrentPositionOnce()).rejects.toMatchObject({
+      name: 'GeoOnceError',
+      code: 'unsupported',
+    });
+  });
+
+  it('FE-HOOK-GEO-022: rejects outside a secure context without asking the browser', async () => {
+    const getCurrentPosition = vi.fn();
+    stubOnce(getCurrentPosition);
+    vi.stubGlobal('isSecureContext', false);
+
+    await expect(getCurrentPositionOnce()).rejects.toMatchObject({ code: 'insecure-context' });
+    expect(getCurrentPosition).not.toHaveBeenCalled();
+  });
+
+  it.each([
+    [1, 'permission-denied'],
+    [2, 'unavailable'],
+    [3, 'timeout'],
+  ])('FE-HOOK-GEO-023: maps error code %i to "%s"', async (code, expected) => {
+    stubOnce((_ok, fail) => fail?.(geoError(code)));
+
+    const rejection = await getCurrentPositionOnce().catch((e: unknown) => e);
+    expect(rejection).toBeInstanceOf(GeoOnceError);
+    expect((rejection as GeoOnceError).code).toBe(expected);
+  });
+});