Fixed world clock: no player time controls (ISS-117)

The world always runs at WORLD_TIME_SCALE = 24 (lib/worldClock.ts). A server
background tick (instrumentation.ts -> startBackgroundTick, 1 s interval)
advances the sim with no open browser; idle-pause freezes the clock exactly
while no plane is flying or in repair. Fresh worlds start year 2000
(STARTING_CLOCK_MS in seed.ts).

- Removed: POST /api/sim + OpenAPI entry, applyTimeControls/clampTimeScale,
  lib/timeScale.ts, LeftPane pause button + scale slider machinery,
  ISS-057 slow-on-landing/resume in flyPlane.
- Snapshot simState is now { clockMs } only; client extrapolates at the fixed
  rate between polls and freezes while idle (useSimClock).
- New test-only hook POST /api/test/set-timescale behind FLIGHT_TEST_HOOKS=1
  (sibling of set-health); all e2e setScale helpers call it, afterEach restores
  the world rate. E2E pause tests replaced by idle-pause assertions; sim.spec.ts
  activates the world via set-health + /repair for advance/expiry tests.

app/api/state/route.test.ts

@@ -43,10 +43,8 @@ describe('GET /api/state', () => {
     expect(typeof account.cash).toBe('number');
     expect(typeof account.reputation).toBe('number');
 
-    const sim = body.simState as { clockMs: number; timeScale: number; paused: boolean };
+    const sim = body.simState as { clockMs: number }; // ISS-117: time controls are gone — clock only
     expect(typeof sim.clockMs).toBe('number');
-    expect(typeof sim.timeScale).toBe('number');
-    expect(sim.paused).toBe(false);
 
     const planes = body.planes as Array<Record<string, unknown>>;
     expect(planes.length).toBeGreaterThanOrEqual(1);