feat: add context.maybePop() for Navigator-first back handling

[Mastersam07]

closes #59

[github-actions]

📖 Docs preview: https://kaisel.dev/pr-76/ (updates on every push; removed when this PR closes)

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 99.95%. Comparing base (55ee3ec) to head (e8eaa46).

Files with missing lines	Patch %	Lines
packages/kaisel/lib/src/kaisel_scope.dart	80.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##               dev      #76      +/-   ##
===========================================
- Coverage   100.00%   99.95%   -0.05%     
===========================================
  Files           42       42              
  Lines         2322     2327       +5     
===========================================
+ Hits          2322     2326       +4     
- Misses           0        1       +1     

Flag	Coverage Δ
kaisel	99.95% <80.00%> (-0.05%)	⬇️
kaisel_core	99.95% <80.00%> (-0.05%)	⬇️
kaisel_devtools	99.95% <80.00%> (-0.05%)	⬇️
kaisel_lint	99.95% <80.00%> (-0.05%)	⬇️

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