Title: Add structured logging and session telemetry (opt-in)

[Mkalbani]

Description

There is currently no way to diagnose player-reported issues (e.g. "hint gave wrong answer") without reproducing locally. Add structured, opt-in logging that records session events for debugging, with no telemetry sent anywhere by default.

Acceptance Criteria

• tracing crate integrated with structured spans for session start/end, answer submission, and hint reveal
• --debug-log <path> CLI flag writes JSON-lines logs to a file; logging is off by default
• No logs are transmitted over the network under any configuration
• Log format documented in docs/logging.md
• Sensitive data (if any) is excluded or redacted from logs

[Menjay7]

Hi! I came across this issue and would love to work on it. I have experience with similar tasks and I'm confident I can investigate, implement a clean solution, and thoroughly test it before submitting a PR. If the issue is still open, I would appreciate it if you could assign it to me. I’ll prioritize this immediately and ensure a reliable solution is delivered as soon as possible. Thank you!

[VerifiedFlemzy1]

Hello boss, Please assign this issue to me. I checked it out and I am confident I will solve it
my eta is 2 hours

[Menjay7]

Hi! I came across this issue and would love to work on it. I have experience with similar tasks and I'm confident I can investigate, implement a clean solution, and thoroughly test it before submitting a PR. If the issue is still open, I would appreciate it if you could assign it to me. I’ll prioritize this immediately and ensure a reliable solution is delivered as soon as possible. Thank you!

[VerifiedFlemzy1]

Hello boss, Please assign this issue to me. I checked it out and I am confident I will solve it
my eta is 2 hours

[jaynomyaro]

Hi! I’m a full-stack developer with a strong blockchain background, and I’m confident I can resolve this issue quickly and effectively. I’ll deliver a clean, reliable solution with immediate attention to detail, ensuring it’s completed as soon as possible. Please assign it to me—I’m ready to get started right away.

[VerifiedFlemzy1]

Hello boss, Please assign this issue to me. I checked it out and I am confident I will solve it
my eta is 2 hours