docs: add failure recovery runbook for issue #808

[Rayhab2000]

Document practical recovery procedures for common NotifyChain failures:

• Listener interruption: safe restart, stale lock release, prevention
• RPC failures: detect, diagnose, fallback RPC switching
• Database downtime: integrity checks, migration, corruption recovery
• Stuck notification jobs: lock release, bulk re-queue, config tuning
• Failed notification delivery: Discord webhook fix, retry backoff
• Event backfill: cursor reset, selective range backfill, dedup safeguards

Closes #808

Overview

Related Issue

Closes #

Changes

Verification

# e.g.
cd dashboard && npm test
cd listener && npm run typecheck && npm test
cd contract/contracts/hello-world && cargo test

How to Test

Checklist

• Branch is up to date with main
• Tests added/updated and all pass locally
• cargo fmt --all run (if Rust changes)
• npm run lint passes (if TypeScript changes)
• Documentation updated if behavior changed

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@Rayhab2000 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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