[frontend] hide create widget button for read-only dashboard (#6464)

[marieflorescontact]

Proposed changes

• check if current user has edit right for current dashboard

Related issues

• issue/6464

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.70%. Comparing base (c08cb0e) to head (438aba6).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6511   +/-   ##
=======================================
  Coverage   67.70%   67.70%           
=======================================
  Files         532      532           
  Lines       64989    64989           
  Branches     5444     5444           
=======================================
  Hits        43998    43998           
  Misses      20991    20991           

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