Add example runbook for database connection pool exhaustion

[manthan787]

Description

Add an example runbook for diagnosing and resolving database connection pool exhaustion issues.

Context

We have example runbooks in examples/runbooks/ but could use more real-world scenarios to help new users understand the runbook format and best practices.

What to do

1. Create a new file examples/runbooks/database-connection-pool.md
2. Include frontmatter with:
   • type: runbook
   • services: relevant database services
   • symptoms: common error messages like "Connection pool exhausted", "Too many connections"
   • severity: appropriate level
3. Include sections for:
   • Symptoms
   • Quick Diagnosis (queries to check connection counts, idle connections)
   • Mitigation Steps
   • Root Cause Analysis
   • Prevention

Resources

• Look at existing runbooks in examples/runbooks/ for format reference
• See .runbook/runbooks/ for more examples

Getting Started

bun install
bun run dev knowledge search "connection pool"  # Test your runbook is indexed

This is a great first contribution! No code changes required, just markdown.