Wipe out UI state on manual reload

[podliashanyk]

Closes #100

Implemented changes:

Every time the events page is initially loaded, or manually reloaded, the UI state is cleared:

• checked (selected) rows become unchecked
• expanded rows collapse
• any existing error alerts are removed
• list with IDs of current events is cleared (not visible in the UI, related to NTIE table refresh in Table refresh with ntie #87)

[github-actions]

Test results

  4 files    4 suites   8s ⏱️
14 tests 14 ✔️ 0 💤 0 ❌
56 runs  56 ✔️ 0 💤 0 ❌

Results for commit 705b502.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 14.28571% with 6 lines in your changes are missing coverage. Please review.

Please upload report for BASE (main@ec4cc21). Learn more about missing BASE report.

Files	Patch %	Lines
src/howitz/endpoints.py	14.28%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #106   +/-   ##
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  Coverage        ?   50.18%           
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  Files           ?       15           
  Lines           ?      811           
  Branches        ?        0           
=======================================
  Hits            ?      407           
  Misses          ?      404           
  Partials        ?        0           

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