feat(core): add secure recipe APIs, precise scaling and versioned imports

tests/unit/cooking.test.ts

@@ -0,0 +1,20 @@
+import { describe, it, expect } from 'vitest';
+import { startTimer, pauseTimer, remainingMs } from '../../src/lib/cooking';
+describe('Timestamp-based kitchen timers', () => {
+  it('does not display an extra second when the last render predates the start', () => {
+    expect(remainingMs(startTimer({ remaining: 60000, endAt: null }, 1200), 1000)).toBe(60000);
+  });
+  it('starts with an absolute deadline, not ticking state', () => {
+    expect(startTimer({ remaining: 60000, endAt: null }, 1000).endAt).toBe(61000);
+  });
+  it('survives navigation, sleep and serialized progress', () => {
+    const timer = JSON.parse(JSON.stringify(startTimer({ remaining: 60000, endAt: null }, 1000)));
+    expect(remainingMs(timer, 41000)).toBe(20000);
+    expect(remainingMs(timer, 90000)).toBe(0);
+  });
+  it('pauses precisely and resumes without drift', () => {
+    const paused = pauseTimer(startTimer({ remaining: 60000, endAt: null }, 1000), 21000);
+    expect(remainingMs(paused, 90000)).toBe(40000);
+    expect(remainingMs(startTimer(paused, 90000), 100000)).toBe(30000);
+  });
+});