Fix AppCode schema and telemetry for updated dependencies

[RAprogramm]

Summary

• implement a manual utoipa schema for AppCode to keep the OpenAPI feature compiling after the dependency refresh
• emit owned label values before incrementing the error_total counter so metrics 0.24 accepts runtime codes
• relax tonic metadata formatting to avoid new 'static borrow requirements and bump the crate to 0.24.4 with changelog/README updates

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 +1.90.0 audit
• cargo +1.90.0 deny check

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https://chatgpt.com/codex/tasks/task_e_68d7bdde273c832b837fe7b6f631a702