Ensure self._start_time always exists

[puddly]

The bot review on #3 (in a roundabout manner) turned out to be a real issue, not a false positive: a bad tunables configuration caused this exact bug to occur.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (77579c9) to head (04556d5).

Additional details and impacted files

@@            Coverage Diff            @@
##               dev        #5   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            7         7           
  Lines         1679      1681    +2     
=========================================
+ Hits          1679      1681    +2     

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[Copilot]

Pull request overview

Fixes a runtime crash in ControllerApplication.send_packet() by ensuring _start_time is always defined and guarding against cases where network startup did not set it (e.g., due to a bad tunables configuration).

Changes:

• Initialize self._start_time in __init__ to avoid missing-attribute failures.
• Reset self._start_time on disconnect().
• Update the route-hint startup-window check in send_packet() to tolerate _start_time being unset.

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