fix: fill the problem 309 cooldown profits from the end - #5945

Summary

Problem 309 method 1 always recurses to the next day. With up to 5,000 prices that chain overflows Python's call stack. Python, Java, C++, Go, and TypeScript now fill the same holding-state table from the end. Methods 2 and 3 still use the forward formulation.

Type

• New solution
• Update solution
• Docs
• Other

Checklist

For new or updated solutions:

• README.md / README_EN.md follow solution/template.md
• If a Thinking block is added, it sits after the method heading, is non-empty, and matches the code in the repo (naive idea vs constraints, bottleneck, key observation, why this method). Thinking is optional.
• All languages implement the same algorithm; unrelated Solution.* files and code tabs are unchanged
• Code is formatted as described in AGENTS.md