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.

lib/db/client.test.ts

@@ -3,6 +3,8 @@ import os from 'node:os';
 import path from 'node:path';
 import initSqlJs from 'sql.js';
 import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import { WORLD_TIME_SCALE } from '@/lib/worldClock';
+import { STARTING_CLOCK_MS } from '@/lib/game/seed';
 import { openGameDb, persist } from './client';
 import * as schema from './schema';
 
@@ -111,8 +113,9 @@ describe('openGameDb', () => {
     const account = (await inst.db.select().from(schema.account))[0];
     expect(account?.cash).toBeGreaterThan(0);
     const sim = (await inst.db.select().from(schema.simState))[0];
-    expect(sim?.paused).toBe(false);
-    expect(sim?.timeScale).toBe(1);
+    // ISS-117: fresh worlds start at the year-2000 game clock with the fixed world rate.
+    expect(sim?.clockMs).toBe(STARTING_CLOCK_MS);
+    expect(sim?.timeScale).toBe(WORLD_TIME_SCALE);
 
     // The seed was durably written: the file exists and is non-empty.
     const st = await fs.stat(file);