Add telemetry hook and optional error metrics

[RAprogramm]

Summary

• add an AppError::emit_telemetry hook that captures backtraces lazily, records metrics and emits tracing events exactly once per error
• wire constructors, context conversions and framework integrations through the telemetry hook so HTTP responses flush instrumentation automatically
• add optional metrics/log-mdc dependencies, bump the crate to 0.14.0, refresh docs and expand tests to cover tracing MDC propagation and counter increments

Testing

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

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https://chatgpt.com/codex/tasks/task_e_68d210622424832bbbf643d917c07023