fix(dotcom): suppress confusing KV error output in feature flags test (tldraw#8405)

The KV error fallback test in `featureFlags.test.ts` intentionally
throws to verify graceful degradation, but the `console.error` from the
catch block was showing up in CI output and looked like a real failure:

```
Failed to get feature flag zero_kill_switch: Error: KV down
    at Object.<anonymous> (.../featureFlags.test.ts:170:10)
```

This suppresses the expected `console.error` during the test. 

Example run
[here](https://github.com/tldraw/tldraw/actions/runs/23846844691/job/69516189133?pr=8031#step:15:894).

### Change type

- [x] `improvement`

### Test plan

- [x] Unit tests

### Code changes

| Section | LOC change |
| ------- | ---------- |
| Tests   | +2 / -0   |

Author: MitjaBezensek

apps/dotcom/client/src/tla/utils/FeatureFlagPoller.test.ts

@@ -115,6 +115,9 @@ describe('fetchFeatureFlags', () => {
 		mockFetch.mockReset()
 		// Module-level fetchFeatureFlags() fires on import. Use an unauthenticated
 		// response so the promise cache is cleared and each test starts fresh.
+		// Two responses needed: one for the module-level call, one for the explicit await
+		// (the unauthenticated response clears the cache, so the second call refetches).
+		mockFetchResponse(makeFlags(), false)
 		mockFetchResponse(makeFlags(), false)
 		const mod = await import('./FeatureFlagPoller')
 		fetchFeatureFlags = mod.fetchFeatureFlags
@@ -152,17 +155,21 @@ describe('fetchFeatureFlags', () => {
 	})
 
 	it('returns default flags on fetch error', async () => {
+		const spy = vi.spyOn(console, 'error').mockImplementation(() => {})
 		mockFetch.mockRejectedValueOnce(new Error('network down'))
 		const flags = await fetchFeatureFlags()
 		expect(flags.zero_kill_switch.enabled).toBe(false)
 		expect(flags.zero_enabled.enabled).toBe(false)
 		expect(wasAuthenticated()).toBe(false)
+		spy.mockRestore()
 	})
 
 	it('returns default flags on non-ok response', async () => {
+		const spy = vi.spyOn(console, 'error').mockImplementation(() => {})
 		mockFetch.mockResolvedValueOnce({ ok: false, status: 500 })
 		const flags = await fetchFeatureFlags()
 		expect(flags.zero_kill_switch.enabled).toBe(false)
 		expect(flags.zero_enabled.enabled).toBe(false)
+		spy.mockRestore()
 	})
 })

apps/dotcom/sync-worker/src/utils/featureFlags.test.ts

@@ -165,12 +165,14 @@ describe('getFeatureFlagValue', () => {
 	})
 
 	it('returns defaults on KV error', async () => {
+		const consoleSpy = vi.spyOn(console, 'error').mockImplementation(() => {})
 		const env = makeEnv()
 		env.FEATURE_FLAGS.get = vi.fn(async () => {
 			throw new Error('KV down')
 		})
 		const value = await getFeatureFlagValue(env as any, 'zero_kill_switch')
 		expect(value).toMatchObject({ type: 'boolean', enabled: false })
+		consoleSpy.mockRestore()
 	})
 })