Add OpenTelemetry tracing bootstrap to shoppingassistantservice

[Jason59000]

What

Adds an OpenTelemetry bootstrap module for shoppingassistantservice with OTLP export, service.name=shoppingassistantservice, and Flask instrumentation. The Docker entrypoint loads the bootstrap before importing the Flask application so incoming requests are traced automatically.

Why

Shopping Assistant has no tracing SDK, exporter, resource, or framework instrumentation despite making high-latency calls to Gemini and AlloyDB. Baseline request tracing provides immediate latency and error visibility while keeping prompts, images, retrieved documents, and credentials out of span attributes.

Caveats

• Export configuration uses standard OpenTelemetry environment variables.
• Custom GenAI and database spans are intentionally deferred until a privacy-safe attribute policy is reviewed.
• Regenerate requirements.txt from requirements.in during review.
• Existing tests are not modified.