Add alphanumeric CNPJ support

[pnzrfst]

Summary

• Update format_regex in Cnpj to accept uppercase alphanumeric characters ([A-Z0-9]) in the first 12 positions, keeping check digits as numeric-only
• Update format_number in Cnpj to use number_without_mask with an alphanumeric-aware regex
• Update reduce_weights in Mod11 to use char.ord - 48 instead of char.to_i, enabling correct weight calculation for letter characters — backwards-compatible for CPF since digits produce identical results under both approaches

Test plan

• Valid alphanumeric CNPJ passes (unformatted and formatted)
• Invalid alphanumeric CNPJ with wrong check digit is rejected
• Lowercase alphanumeric input is rejected
• All existing numeric CNPJ and CPF specs continue to pass

🤖 Generated with Claude Code

[qltysh]

Coverage Impact

This PR will not change total coverage.

Modified Files with Diff Coverage (4)

Rating	File	% Diff	Uncovered Line #s
	lib/br_documents/cnpj_cpf/document.rb	100.0%
	lib/br_documents/cnpj_cpf/cnpj.rb	100.0%
	lib/br_documents/suframa.rb	100.0%
	lib/br_documents/commons/mod11.rb	100.0%
	Total	100.0%

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• Diff Coverage: Coverage for added or modified lines of code (excludes deleted files). Learn more.

• Total Coverage: Coverage for the whole repository, calculated as the sum of all File Coverage. Learn more.

• File Coverage: Covered Lines divided by Covered Lines plus Missed Lines. (Excludes non-executable lines including blank lines and comments.)

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