fix: avoid trapping on non-finite prefetch TTLs and disable hits for TTL <= 0

[huytdps13400]

Fixes #196

Root cause

• iOS crash: the three FetchCache.getResultIfFresh call sites in HybridNitroFetchClient.swift converted the TTL with Int64(req.prefetchCacheTtlMs ?? 5_000). Swift's Int64(Double) traps on NaN, ±Infinity and values outside the Int64 range. typeof NaN === 'number', so prefetchCacheTtlMs: NaN or Infinity passed from JS (or an NSNumber passed to NitroAutoPrefetcher.registerPrefetch) crashes the app. Android's Double.toLong() saturates instead, so it doesn't crash there.
• Zero TTL can still hit: both caches checked only age <= maxAgeMs. When the response completed in the same millisecond, age is 0, so a TTL of 0 returned a hit. The docs say a value <= 0 disables cache hits. On Android, NaN.toLong() is 0, so a NaN TTL hit the same way.

Changes

• ios/FetchCache.swift: getResultIfFresh now takes maxAgeMs: Double and compares Double(age) <= maxAgeMs, so there's no trapping conversion. It also requires maxAgeMs > 0. The three call sites pass req.prefetchCacheTtlMs ?? 5_000 directly.
• android/.../FetchCache.kt: getResultIfFresh and hasFreshResult also require maxAgeMs > 0.
• docs-website/docs/prefetch.md: I removed the parenthetical that described the old age <= maxAgeMs mechanism.

After this change both platforms handle unusual TTLs the same way: <= 0, NaN and -Infinity never hit, Infinity (and huge values) never expire, and ordinary TTLs work as before. Joining an in-flight prefetch still works whatever the TTL. The JS builders are unchanged.

Verification

I couldn't drive the full prefetch flow on a device in this environment. Instead I tested the real FetchCache.swift and FetchCache.kt files in small standalone harnesses, with a stub NitroResponse and the same call-site expressions:

TTL	iOS before	iOS after	Android before	Android after
0 (same ms)	hit	miss	hit	miss
NaN	crash (SIGTRAP, exit 133)	miss	hit	miss
Infinity	crash (SIGTRAP, exit 133)	hit	hit	hit
1e19	crash (SIGTRAP, exit 133)	hit	n/a	n/a
-5 / -1	miss	miss	miss	miss
60000	hit	hit	hit	hit

Other checks:

• ./gradlew :react-native-nitro-fetch:compileDebugKotlin in example/android passes.
• xcodebuild -scheme NitroFetch -sdk iphonesimulator (Debug, arm64) for the NitroFetch pod in the example workspace succeeds.
• bun typecheck, bun lint (0 errors) and bun test all pass.

Platforms: iOS (crash and zero-TTL fix) and Android (zero-TTL fix).

This fix was prepared with AI assistance (Claude Code) and verified locally with the tests above.

🤖 Generated with Claude Code

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[riteshshukla04]

Thanks