Add opt-in OpenTelemetry tracing hooks

[Mekussdev]

Summary

• Add optional OpenTelemetry tracing for HTTP, Express, and NestJS.
• Export spans over OTLP/HTTP and shut down the SDK with the application.
• Keep tracing disabled unless OTEL_TRACING_ENABLED=true.
• Document configuration and add tests for the default-off setting.

Verification

• Focused tests: 25 passed.
• Changed-file lint and SDK start/shutdown check passed.
• Full repository checks have existing failures: one ticket test, TypeScript/build errors, generated API docs, and dependency audit findings.

closes #181

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