feat: add solutions to lc problem: No.3756

[yanglbme]

Summary

• Add prefix sum solutions for LeetCode 3756 in Python, Java, C++, Go, and TypeScript
• Update README.md and README_EN.md with solution explanations and code blocks

Test plan

• Code formatted with black, clang-format, gofmt, and prettier
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[Copilot]

Pull request overview

This PR adds multi-language reference solutions for LeetCode 3756. Concatenate Non-Zero Digits and Multiply by Sum II, using a prefix-sum / prefix-concatenation approach, and updates the problem READMEs with the corresponding explanation and code snippets.

Changes:

• Add solution implementations in Python, Java, C++, Go, and TypeScript.
• Document the prefix arrays + modular arithmetic derivation in README.md and README_EN.md.
• Include full code blocks for all supported languages in both READMEs.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
solution/3700-3799/3756.Concatenate Non-Zero Digits and Multiply by Sum II/Solution.ts	TypeScript solution using prefix arrays and bigint modular arithmetic.
solution/3700-3799/3756.Concatenate Non-Zero Digits and Multiply by Sum II/Solution.py	Python solution using prefix arrays and modular arithmetic.
solution/3700-3799/3756.Concatenate Non-Zero Digits and Multiply by Sum II/Solution.java	Java solution with precomputed powers of 10 and O(1) queries.
solution/3700-3799/3756.Concatenate Non-Zero Digits and Multiply by Sum II/Solution.go	Go solution with precomputed powers of 10 and prefix tracking.
solution/3700-3799/3756.Concatenate Non-Zero Digits and Multiply by Sum II/Solution.cpp	C++ solution with static power table and prefix arrays.
solution/3700-3799/3756.Concatenate Non-Zero Digits and Multiply by Sum II/README.md	Chinese explanation + embedded code for all languages.
solution/3700-3799/3756.Concatenate Non-Zero Digits and Multiply by Sum II/README_EN.md	English explanation + embedded code for all languages.

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