feat: sync calendar instantly on changes

[st3iny]

This approach requires notify_push.

[codecov[bot]]

Codecov Report

:x: Patch coverage is 0% with 39 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 12.96%. Comparing base (b3f9102) to head (e0eb03d). :warning: Report is 30 commits behind head on main.

Files with missing lines	Patch %	Lines
src/store/calendars.js	0.00%	16 Missing and 2 partials :warning:
src/services/notifyService.ts	0.00%	14 Missing :warning:
src/views/Calendar.vue	0.00%	7 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6364      +/-   ##
==========================================
- Coverage   13.02%   12.96%   -0.06%     
==========================================
  Files         224      225       +1     
  Lines       11634    11684      +50     
  Branches     2797     2828      +31     
==========================================
  Hits         1515     1515              
- Misses       9759     9807      +48     
- Partials      360      362       +2     

Flag	Coverage Δ
javascript	12.96% <0.00%> (-0.06%)	:arrow_down:

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[tcitworld]

This is nice, but I feel working with Sabre's DAV Push to use WebPush would be half the work and bring the same functionality to 3rd-party clients for the same cost?