feat(telemetry): add otel analytics ingestion and export

[tyulyukov]

Summary

• Add an OTEL trace ingest route in apps/landing that sanitizes incoming payloads, enforces size/rate limits, and forwards to the configured collector.
• Add Jira-token-backed identity verification for Genesis users, including a proof header flow and cached verification for OTEL ingest.
• Add server-side product analytics export for browser traces, enriched with user, app, and platform metadata before forwarding to the product analytics endpoint.
• Record new analytics events for project, thread, provider, and git PR/MR activity, with config plumbing for MARCODE_PRODUCT_ANALYTICS_TRACES_URL and fallback routing.
• Update landing copy and tracing-related web/server integrations to match the new analytics flow.

Testing

• Not run (not requested).
• Added new Vitest coverage for OTEL ingest sanitization, rate limiting, Genesis detection, and collector forwarding.
• Updated server tests to cover the new analytics config shape and telemetry plumbing.