fix: race conditions and memory leaks in validator names and frontend cache

[Sahil-4555]

What's the problem?

Found two bugs that can cause crash:

1. Validator names service crashes every 6 hours - Background job and HTTP requests were accessing same maps without proper locks
2. Memory leak from stuck goroutines - Timeout handling was leaving worker goroutines blocked forever

How does the race happen?

For validator names:

• Background updater runs resolveNames() every 6 hours (takes ~60 seconds)
• Meanwhile, users visiting /validators page call GetValidatorName()
• Both access same maps: resolveNames() writes without lock, GetValidatorName() reads WITH lock
• Go panics: fatal error: concurrent map read and map write -> crash

For frontend cache:

• Slow page loads timeout after 30s, main goroutine returns
• Worker goroutine completes later, tries sending to unbuffered channel
• No one listening anymore -> worker blocks forever -> memory leak
• Plus isTimedOut boolean had data race