Speedup data reading

[renecotyfanboy]

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📚 Documentation preview 📚: https://jaxspec--139.org.readthedocs.build/en/139/

[codecov]

Codecov Report

Attention: Patch coverage is 96.82540% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 89.72%. Comparing base (3191cee) to head (25b3708).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/jaxspec/data/obsconf.py	97.14%	1 Missing ⚠️
src/jaxspec/data/observation.py	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #139      +/-   ##
==========================================
+ Coverage   89.70%   89.72%   +0.02%     
==========================================
  Files          17       17              
  Lines        1107     1119      +12     
==========================================
+ Hits          993     1004      +11     
- Misses        114      115       +1     

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