shoestring: add gettext fallback=True to avoid missing messages error

[u2yasan]

Fixes missing translation files by adding fallback=True to gettext.translation calls in both the main CLI and the wizard.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.26%. Comparing base (c028861) to head (04293a8).
Report is 2 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1472      +/-   ##
==========================================
- Coverage   98.28%   98.26%   -0.02%     
==========================================
  Files         164      159       -5     
  Lines        6770     6636     -134     
  Branches      143      143              
==========================================
- Hits         6654     6521     -133     
+ Misses        116      115       -1     

Flag	Coverage Δ
explorer-rest	?
tools-shoestring	97.03% <100.00%> (ø)

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Files with missing lines	Coverage Δ
tools/shoestring/shoestring/__main__.py	97.61% <100.00%> (ø)

... and 5 files with indirect coverage changes

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