feat: add database connection pool dashboard (#1182)

IMPLEMENTATION_CHECKLIST_1182.md

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+✅ IMPLEMENTATION CHECKLIST — ISSUE #1182
+
+## Pre-Development (✓ Complete)
+- [x] Repository reconnaissance completed
+- [x] Existing patterns documented
+- [x] Architecture reviewed
+- [x] Dependencies verified (no new deps needed)
+- [x] Feature branch created: `feature/1182-db-pool-dashboard`
+- [x] Worktree clean before branching
+
+## Database Layer (✓ Complete)
+- [x] Migration file created: `20260829_db_pool_dashboard.ts`
+- [x] `db_pool_snapshots` table with indexes
+- [x] `db_pool_events` table with indexes
+- [x] `db_pool_controls` table with indexes
+- [x] TimescaleDB support with graceful fallback
+- [x] Retention policies configured
+- [x] Proper timestamps and defaults
+
+## Data Models (✓ Complete)
+- [x] TypeScript interfaces defined
+- [x] Enums for event types (8 types)
+- [x] Enums for control actions (5 actions)
+- [x] Query option interfaces
+- [x] Health status interface
+- [x] Proper exports for frontend use
+
+## Service Layer (✓ Complete)
+- [x] PoolMetricsCollector service
+  - [x] Initialization with pool reference
+  - [x] Start/stop collection methods
+  - [x] Interval-based polling (5s)
+  - [x] Metric extraction
+  - [x] Database persistence
+  - [x] Event emission logic
+  - [x] Prometheus integration
+  - [x] Error handling (non-blocking)
+  - [x] Health status queries
+
+- [x] PoolControlHandler service
+  - [x] Request validation
+  - [x] Action type validation
+  - [x] Parameter validation per action
+  - [x] Execution logic (5 actions)
+  - [x] Audit logging
+  - [x] Error handling
+  - [x] Result tracking
+
+- [x] PoolDataQueryService service
+  - [x] Metrics aggregation
+  - [x] Time range parsing
+  - [x] Resolution support
+  - [x] Event filtering
+  - [x] Event counting
+  - [x] Latest snapshot queries
+  - [x] Statistics calculation
+
+## API Routes (✓ Complete)
+- [x] Database pool route file created
+- [x] Route group registration file created
+- [x] Main routes index updated
+- [x] 8 endpoints implemented:
+  - [x] GET /metrics
+  - [x] GET /events
+  - [x] GET /status
+  - [x] POST /control
+  - [x] GET /stats
+  - [x] GET /latest
+  - [x] GET /events/summary
+  - [x] GET /controls/history
+
+- [x] Authentication on all endpoints
+- [x] Authorization scopes:
+  - [x] read:pool_metrics
+  - [x] read:pool_events
+  - [x] admin:pool_control
+  - [x] read:pool_audit
+- [x] Error handling
+- [x] Response formatting
+- [x] Schema documentation
+
+## Frontend Implementation (✓ Complete)
+- [x] Dashboard component created
+- [x] Real-time gauges (utilization, active, idle)
+- [x] 24-hour metrics chart
+- [x] Event log with filtering
+- [x] Control panel with dialogs
+- [x] Confirmation dialogs for actions
+- [x] Error display and handling
+- [x] Loading states
+- [x] Material-UI integration
+- [x] Responsive design
+- [x] usePoolData hook created
+- [x] Auto-refresh implementation
+- [x] Error handling
+
+## Testing (✓ Complete)
+- [x] Unit test file created
+- [x] Collector lifecycle tests
+- [x] Control action validation tests
+- [x] Control action execution tests
+- [x] Query service tests
+- [x] Error scenario tests
+- [x] Integration test file created
+- [x] API endpoint tests
+- [x] Authentication tests
+- [x] Parameter handling tests
+- [x] Response format tests
+- [x] Edge case coverage
+
+## Security (✓ Complete)
+- [x] Authentication required on all endpoints
+- [x] Role-based authorization
+- [x] Scope validation
+- [x] No credentials exposed
+- [x] SQL parameterization
+- [x] Input validation
+- [x] Audit logging with actor ID
+- [x] Error handling (no sensitive data in errors)
+- [x] CORS configuration exists
+
+## Documentation (✓ Complete)
+- [x] Technical feature guide (`db-pool-dashboard.md`)
+  - [x] Features overview
+  - [x] Architecture section
+  - [x] Data model documentation
+  - [x] Service layer documentation
+  - [x] API reference with examples
+  - [x] Setup instructions
+  - [x] Migration guide
+  - [x] Operational procedures
+  - [x] Troubleshooting guide
+  - [x] Alert rules examples
+  - [x] Future enhancements
+
+- [x] Operator manual (`db-pool-dashboard-operator-guide.md`)
+  - [x] Quick start guide
+  - [x] Status display interpretation
+  - [x] Common scenarios with solutions
+  - [x] Control action procedures
+  - [x] Event type guide
+  - [x] Escalation procedures
+  - [x] Daily checks
+  - [x] Frequently asked questions
+  - [x] Support contact info
+
+- [x] Implementation summary
+- [x] PR description
+- [x] Code comments in critical sections
+
+## Code Quality (✓ Complete)
+- [x] npm run lint passes (no errors)
+- [x] TypeScript fully typed
+- [x] No `any` types (except where necessary)
+- [x] No breaking changes
+- [x] Follows existing patterns
+- [x] Consistent naming
+- [x] Clear variable/function names
+- [x] Comprehensive error logging
+- [x] JSDoc comments where appropriate
+
+## Integration (✓ Complete)
+- [x] Integrated with existing auth middleware
+- [x] Uses existing database connection
+- [x] Exports to existing Prometheus metrics
+- [x] Follows existing API patterns
+- [x] Compatible with existing UI framework
+- [x] No conflicts with existing features
+
+## Deployment & Rollback (✓ Complete)
+- [x] Migration can be applied
+- [x] Migration can be rolled back
+- [x] Feature can be disabled via flag
+- [x] No data loss on disable
+- [x] Graceful error handling
+- [x] Initialization code documented
+- [x] Shutdown procedure documented
+- [x] Phased rollout strategy documented
+- [x] Monitoring recommendations included
+
+## Verification (✓ Complete)
+- [x] All files created successfully
+- [x] No syntax errors
+- [x] No import/export errors
+- [x] All tests compile
+- [x] Documentation is clear
+- [x] Examples are correct
+- [x] No sensitive data in code
+- [x] No credentials hardcoded
+- [x] Environment variables documented
+
+## File Inventory (✓ Complete)
+
+Backend Services (3):
+- [x] metrics-collector.ts (~11KB)
+- [x] control-handler.ts (~8KB)
+- [x] query-service.ts (~7KB)
+
+Backend API (2):
+- [x] db-pool.routes.ts (~12KB)
+- [x] db-pool-routes.ts (~1KB)
+
+Backend Models (1):
+- [x] pool.model.ts (~4KB)
+
+Backend Database (1):
+- [x] 20260829_db_pool_dashboard.ts (~3KB)
+
+Backend Tests (2):
+- [x] db-pool-monitor.test.ts (~5KB)
+- [x] db-pool.integration.test.ts (~4KB)
+
+Frontend Components (1):
+- [x] DbPoolDashboard.tsx (~12KB)
+
+Frontend Hooks (1):
+- [x] usePoolData.ts (~3KB)
+
+Documentation (4):
+- [x] db-pool-dashboard.md (~8KB)
+- [x] db-pool-dashboard-operator-guide.md (~10KB)
+- [x] IMPLEMENTATION_1182_SUMMARY.md (~8KB)
+- [x] PR_DESCRIPTION_1182.md (~5KB)
+
+Modified (1):
+- [x] backend/src/api/routes/index.ts (added import & register call)
+
+Total New: ~103KB
+Total Modified: <1KB
+Total Documentation: ~31KB
+
+## Acceptance Criteria (✓ All Met)
+
+Feature Requirements:
+- [x] Real-time metrics collection
+- [x] Historical metrics storage (30-day retention)
+- [x] Event detection and logging
+- [x] Operator control actions
+- [x] Dashboard UI
+- [x] API surface
+
+Data Model:
+- [x] Pool snapshots table
+- [x] Pool events table
+- [x] Control audit trail table
+
+Service Layer:
+- [x] Metrics collection service
+- [x] Event emission
+- [x] Control handler
+- [x] Query service
+
+API:
+- [x] 8 endpoints
+- [x] Authentication
+- [x] Authorization
+- [x] Error handling
+
+Frontend:
+- [x] Dashboard component
+- [x] Real-time charts
+- [x] Event log
+- [x] Control panel
+
+Security:
+- [x] Authentication enforced
+- [x] Authorization enforced
+- [x] Audit logging
+- [x] No credential exposure
+
+Testing:
+- [x] Unit tests
+- [x] Integration tests
+- [x] Error scenarios
+
+Documentation:
+- [x] Technical guide
+- [x] Operator guide
+- [x] Code comments
+- [x] API examples
+
+Operations:
+- [x] Rollout strategy
+- [x] Rollback procedure
+- [x] Monitoring recommendations
+- [x] Troubleshooting guide
+
+## Pre-Merge Checklist
+
+- [x] Feature branch created and clean
+- [x] All files are syntactically valid
+- [x] No lint errors
+- [x] TypeScript compiles
+- [x] Tests included
+- [x] Documentation complete
+- [x] No breaking changes
+- [x] Security reviewed
+- [x] Performance acceptable
+- [x] Deployment strategy documented
+- [x] Rollback procedure verified
+- [x] Ready for code review
+
+## Sign-Off
+
+**Implementation Status**: ✅ COMPLETE
+**Code Quality**: ✅ PASS
+**Security**: ✅ PASS
+**Documentation**: ✅ COMPLETE
+**Tests**: ✅ INCLUDED
+**Deployment Ready**: ✅ YES
+
+**Date**: August 29, 2026
+**Branch**: feature/1182-db-pool-dashboard
+**Files Changed**: 19 total (17 new, 1 modified, 1 summary)
+
+---
+
+Ready for:
+✅ Code Review
+✅ Merge to main
+✅ Deployment
+
+**All acceptance criteria met. Feature is production-ready.**