feat: make BLQ stale threshold and static friction runtime-configurable

[kylemumma]

This PR is just replacing hardcoded constants with options so I can change the value at runtime. This is necessary for testing in s4s, I dont want to create an actual backlog of 30 minutes, so I will reduce stale threshold to say 4 minutes and test that.

Summary

• Replaces hardcoded BLQ_STALE_THRESHOLD (30m) and BLQ_STATIC_FRICTION (2m) with two sentry-options keys: consumer.blq_stale_threshold_seconds (default 1800) and consumer.blq_static_friction_seconds (default 120).
• BLQRouter now reads both values per-submit() the same way consumer.blq_enabled is read, so they hot-reload without a consumer restart. Friction <= 0 disables friction; friction >= threshold is ignored at runtime.
• Drops the two constants and the corresponding BLQRouter::new arguments from factory_v2.rs.

Test plan

• cargo check clean
• cargo clippy --lib -- -D warnings clean
• cargo test --lib blq_router — 4/4 pass, tests now set thresholds via override_options
• Runtime smoke: with blq_enabled=true and blq_stale_threshold_seconds=5, confirm a 10s-old message routes to BLQ; flip the threshold to 3600 and confirm the next fresh message passes through without restart

🤖 Generated with Claude Code

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