Introduce periodic checks for session schedule times

[davidsteiner]

This isn't the whole flow, but it demonstrates how we can gracefully log out at the end of the session.

[codecov]

Codecov Report

Attention: Patch coverage is 17.85714% with 46 lines in your changes missing coverage. Please review.

Project coverage is 46.43%. Comparing base (2f2f6d8) to head (f8837e6).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/hotfix/src/session.rs	0.00%	28 Missing ⚠️
crates/hotfix/src/session/state.rs	0.00%	11 Missing ⚠️
crates/hotfix/src/session_schedule.rs	71.42%	4 Missing ⚠️
crates/hotfix/src/transport/socket_writer.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #108      +/-   ##
==========================================
- Coverage   46.86%   46.43%   -0.43%     
==========================================
  Files          58       58              
  Lines        2488     2528      +40     
==========================================
+ Hits         1166     1174       +8     
- Misses       1322     1354      +32     

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