apollo_dashboard: widen l1_message_no_successes alert window to 15m

[ShahakShama]

Goal: reduce false-positive pages on the L1 message scraper alert.

Since each sequencer moved to a single L1 provider, the
l1_message_no_successes alert (no successful scrapes within the
window) fires spuriously: a brief gap from the sole provider trips it
even though scraping recovers shortly after. Widening the evaluation
window from 5m to 15m tolerates these short gaps.

Change: bump the increase(l1_message_scraper_success_count[...])
range from 5m to 15m in the alert definition, and regenerate the
matching expression in dev_grafana_alerts.json.

Follow-up (not in this PR): revert to 5m once a fallback mechanism
that switches back to a specific provider per sequencer is in place.

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com

[cursor]

PR Summary

Low Risk
Observability-only tuning of an existing alert threshold/window; no runtime or security behavior changes.

Overview
Widens the l1_message_no_successes alert so it only fires when there are fewer than one successful L1 message scrape over 15 minutes instead of 5 minutes. The Prometheus increase(l1_message_scraper_success_count[...]) range is updated in l1_handlers.rs and the matching rule in dev_grafana_alerts.json.

This is meant to cut false-positive pages after sequencers moved to a single L1 provider, where short provider blips can look like “no successes” in a 5m window even when scraping recovers quickly.

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[reviewable-StarkWare]

This change is 

[ShahakShama]

• apollo_dashboard: widen l1_message_no_successes alert window to 15m #14318 👈 (View in Graphite)
• main-v0.14.3

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[dan-starkware]

@dan-starkware reviewed 2 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on ShahakShama).