Add Vortexa catalog + TechDocs integration

[vortexa-developer-portal]

Adds:

• catalog-info.yaml (with backstage.io/techdocs-ref: dir:.)
• mkdocs.yaml
• docs/index.md

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.19%. Comparing base (a705108) to head (c987884).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #91   +/-   ##
=======================================
  Coverage   88.19%   88.19%           
=======================================
  Files          16       16           
  Lines        1262     1262           
  Branches      143      143           
=======================================
  Hits         1113     1113           
  Misses        111      111           
  Partials       38       38           

Flag	Coverage Δ
unittests	88.19% <ø> (ø)

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