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

[d-Rickyy-b]

Thank you for creating this pull request and making me aware of the underlying issue. Sadly, I cannot merge your PR, since I decided to fix the bug a little bit differently. At the same time I also took care of another issue.