Preserve AppError backtraces when applying context wrappers

[RAprogramm]

Summary

• store captured backtraces on AppError using shared Arc snapshots so existing traces can be reused without cloning
• update ResultExt::context to reuse the shared backtrace when wrapping an existing AppError
• bump the crate version to 0.24.17 and document the fix in the changelog and README

Testing

• cargo +nightly fmt --
• cargo +1.90.0 clippy -- -D warnings
• cargo +1.90.0 build --all-targets
• cargo +1.90.0 test --all
• cargo +1.90.0 doc --no-deps
• cargo audit
• cargo deny check

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https://chatgpt.com/codex/tasks/task_e_68e1ed19b024832b924720b66758db9c