Improve Plotly powder plots with background and clearer hover details

[AndrewSazonov]

Updates Plotly powder measured-vs-calculated plots with improved subplot sizing, matched residual scaling, clearer shared hover labels, explicit trace styling, and an optional background curve. The layout now handles Bragg tick rows more predictably while keeping the main chart easier to read.

[codecov]

Codecov Report

❌ Patch coverage is 98.14815% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.51%. Comparing base (edcdd91) to head (1e2d686).

Files with missing lines	Patch %	Lines
src/easydiffraction/display/plotters/plotly.py	97.95%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #164      +/-   ##
===========================================
+ Coverage    88.42%   88.51%   +0.08%     
===========================================
  Files          154      154              
  Lines         9364     9435      +71     
  Branches       972      979       +7     
===========================================
+ Hits          8280     8351      +71     
  Misses         763      763              
  Partials       321      321              

Flag	Coverage Δ
integration	74.45% <38.88%> (-0.21%)	⬇️
unittests	80.42% <98.14%> (+0.14%)	⬆️

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