use zimfarm UI URL instead of API URL

[elfkuzco]

Changes

• use zimfarm UI URL instead of API URL in env var to construct recipe link

This fixes #426

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.77%. Comparing base (ce87dd1) to head (eb2e35d).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
backend/src/cms_backend/__init__.py	77.77%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #430      +/-   ##
==========================================
+ Coverage   80.69%   80.77%   +0.08%     
==========================================
  Files          64       64              
  Lines        3703     3709       +6     
  Branches      437      436       -1     
==========================================
+ Hits         2988     2996       +8     
+ Misses        576      575       -1     
+ Partials      139      138       -1     

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[benoit74]

Please rather compute and return both links:

• recipe_link is the link to the UI
• recipe_api_link is the link to the API

Quite sure we will need both quite soon ^^

[benoit74]

LGTM, thank you