Add metadata redaction controls and internal formatters

[RAprogramm]

Summary

• add FieldRedaction policies with defaults, new context/app helpers, and document the metadata API
• sanitize problem+json, tonic, and legacy responses using hash/mask rules plus opt-in internal formatters for diagnostics
• extend the derive macro to parse redact(fields(...)), update docs/examples, and expand regression tests

Testing

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

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https://chatgpt.com/codex/tasks/task_e_68d263777988832b82f954b960c5e73b