Fix: detect nested floating-point types

[Jim8y]

Summary

• recursively inspect nested type structures for float, double, and decimal
• apply the same validation to local variables and public signatures
• retain array handling and report the actual unsupported inner type

Why

The floating-point analyzers only inspected direct types and array element types. Generic wrappers such as Tuple<int, double> and Wrapper<float> could bypass the contract diagnostics.

Validation

• floating-point analyzer tests: 7 passed
• complete analyzer unit test suite: 285 passed
• targeted dotnet format --verify-no-changes

Part of #1841.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.22%. Comparing base (11bd7a1) to head (3f905c6).
⚠️ Report is 4 commits behind head on master-n3.

Additional details and impacted files

@@              Coverage Diff              @@
##           master-n3    #1908      +/-   ##
=============================================
- Coverage      84.23%   84.22%   -0.01%     
=============================================
  Files            308      308              
  Lines          28229    28219      -10     
  Branches        3980     3980              
=============================================
- Hits           23778    23768      -10     
  Misses          3459     3459              
  Partials         992      992              

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