Normalize CIF datablock names during import

[AndrewSazonov]

Convert imported CIF datablock names to lowercase and remove unsupported characters while preserving letters, digits, hyphens, and underscores. Directly created structure and experiment names remain strictly validated.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.40%. Comparing base (94970a9) to head (a275cf4).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #223      +/-   ##
===========================================
+ Coverage    90.38%   90.40%   +0.01%     
===========================================
  Files          284      284              
  Lines        24789    24792       +3     
  Branches      2910     2910              
===========================================
+ Hits         22405    22412       +7     
+ Misses        1755     1754       -1     
+ Partials       629      626       -3     

Flag	Coverage Δ
unittests	90.40% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/easydiffraction/io/cif/parse.py	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

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