fix: Restrict eloquent scope and observer functionality based on multitenanted context

[ollieread]

This PR addresses #65 by having all the tenant-child scopes and observers exit only if outside multitenanted context.

[codecov]

Codecov Report

Attention: Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Project coverage is 86.24%. Comparing base (2abfc25) to head (0a39cd4).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/Database/Eloquent/Scopes/TenantChildScope.php	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main      #66      +/-   ##
============================================
- Coverage     86.80%   86.24%   -0.56%     
- Complexity      379      386       +7     
============================================
  Files            57       57              
  Lines          1091     1105      +14     
============================================
+ Hits            947      953       +6     
- Misses          144      152       +8     

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