fix: resolve deadlock in LoadCTIndex when index file doesn't exist

[gnana997]

Problem

LoadCTIndex holds mutex.Lock() and then calls createCTIndexFile(), which attempts to acquire mutex.RLock(), causing a deadlock when the CT index file doesn't exist on first run.

Solution

Restructure the code to:

1. Read the file before acquiring the lock
2. Only hold the lock while marshalling/unmarshalling the index
3. Inline the file creation logic to avoid nested lock acquisition