fix: sync refactor — fix 6 bugs + cache refresh na sync

- setDeletedAt update nu ook updatedAt (bug 2)
- getAllMeasurements filtert deletedAt IS NULL, nieuwe getAllMeasurementsForSync voor sync
- mergeMeasurements detecteert server deleted:true → deletedAt (bug 1)
- syncAll: pull-push split met remoteUpdatedMap, geen double-push (bug 3)
- hard delete alleen na API-succes (bug 4)
- DashboardScreen: refreshCache() na syncAll zodat UI niet op Laden blijft hangen
- deleteMeasurement() dead code verwijderd (bug 5)
- tests: 3 nieuwe testcases voor deleted → deletedAt mapping, 15/15 pass

tests/database.test.ts

@@ -81,7 +81,7 @@ describe('database', () => {
     expect(result!.id).toBe(mockMeasurement.id)
   })
 
-  it('setDeletedAt sets the deletedAt timestamp', async () => {
+  it('setDeletedAt sets both deletedAt and updatedAt timestamps', async () => {
     db.runAsync.mockResolvedValue(undefined)
     await initDatabase()
     await setDeletedAt(mockMeasurement.id)
@@ -89,5 +89,7 @@ describe('database', () => {
       expect.stringContaining('UPDATE measurements SET deletedAt'),
       expect.arrayContaining([mockMeasurement.id])
     )
+    const args = (db.runAsync as jest.Mock).mock.calls.slice(-1)[0]
+    expect(args[1][0]).toBe(args[1][1])
   })
 })