Allow running backend on prefixed url

[evroon]

To run the frontend and backend on the same url, we must prefix the backend calls with e.g. /api to differentiate between frontend and backend requests.

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Deploying bracket-frontend with    Cloudflare Pages

Latest commit:	1e5204c
Status:	✅  Deploy successful!
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[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.77%. Comparing base (f760d6d) to head (7166e4a).

Files with missing lines	Patch %	Lines
backend/bracket/app.py	40.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1495      +/-   ##
==========================================
- Coverage   94.77%   94.77%   -0.01%     
==========================================
  Files         120      120              
  Lines        4363     4379      +16     
==========================================
+ Hits         4135     4150      +15     
- Misses        228      229       +1     

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Deploying bracket-docs with    Cloudflare Pages

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