Fix extractor false positives for Python, Lisp, and Perl

[Widthdom]

Summary

• Mask Python triple-quoted f-string literal text across physical lines while preserving interpolation references.
• Suppress Lisp/Racket quoted reader-macro forms from symbol definition extraction without hiding definitions inside wrappers.
• Normalize and deduplicate Perl hash constant keys, including whitespace, Unicode normalization, and Perl hex escapes.

Validation

• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter "FullyQualifiedNameReferenceExtractorTests.Extract_PythonFString|FullyQualifiedNameSymbolExtractorTests.Extract_CommonLisp|FullyQualifiedName~SymbolExtractorTests.Extract_Perl" -p:UseSharedCompilation=false
• dotnet run --project tools/CodeIndex.Changelog -- check
• dotnet build CodeIndex.sln -c Release -p:UseSharedCompilation=false
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll status --check --json
• codex exec adversarial review: No blocking/actionable issues found.

Fixes #1438
Fixes #2004
Fixes #2005