feat(01-01): create monitoring tables migration

- Add service_health_checks table with status CHECK constraint, JSONB probe_details, checked_at column
- Add alert_events table with alert_type and status CHECK constraints, lifecycle timestamps
- Add created_at indexes on both tables (INFR-01 requirement)
- Add composite indexes for common query patterns
- Enable RLS on both tables (service role bypasses RLS per Supabase pattern)

backend/src/models/migrations/012_create_monitoring_tables.sql

@@ -0,0 +1,64 @@
+-- Migration: Create monitoring tables for service health checks and alert events
+-- Created: 2026-02-24
+-- Purpose: Establish data foundation for the monitoring system.
+--          Phase 1 of the monitoring feature — tables must exist before health probes
+--          or alert services can write data.
+
+-- =============================================================================
+-- TABLE: service_health_checks
+-- Records the result of each health probe run against a monitored service.
+-- =============================================================================
+
+CREATE TABLE IF NOT EXISTS service_health_checks (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    service_name VARCHAR(100) NOT NULL,
+    status TEXT NOT NULL CHECK (status IN ('healthy', 'degraded', 'down')),
+    latency_ms INTEGER,                                          -- nullable: not applicable for all probe types
+    checked_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP, -- when the probe actually ran (distinct from created_at)
+    error_message TEXT,                                          -- nullable: probe failure details
+    probe_details JSONB,                                         -- nullable: flexible metadata (response codes, error specifics, etc.)
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
+);
+
+-- Index required by INFR-01: supports 30-day retention queries
+CREATE INDEX IF NOT EXISTS idx_service_health_checks_created_at
+    ON service_health_checks(created_at);
+
+-- Composite index for dashboard "latest check per service" queries
+CREATE INDEX IF NOT EXISTS idx_service_health_checks_service_created
+    ON service_health_checks(service_name, created_at);
+
+-- Enable RLS (service role key bypasses RLS automatically — explicit policies added in Phase 3)
+ALTER TABLE service_health_checks ENABLE ROW LEVEL SECURITY;
+
+-- =============================================================================
+-- TABLE: alert_events
+-- Tracks alert lifecycle: creation, acknowledgement, and resolution.
+-- =============================================================================
+
+CREATE TABLE IF NOT EXISTS alert_events (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    service_name VARCHAR(100) NOT NULL,
+    alert_type TEXT NOT NULL CHECK (alert_type IN ('service_down', 'service_degraded', 'recovery')),
+    status TEXT NOT NULL CHECK (status IN ('active', 'acknowledged', 'resolved')),
+    message TEXT,                                                -- nullable: human-readable alert description
+    details JSONB,                                               -- nullable: structured metadata about the alert
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+    acknowledged_at TIMESTAMP WITH TIME ZONE,                    -- nullable: set when status → acknowledged
+    resolved_at TIMESTAMP WITH TIME ZONE                         -- nullable: set when status → resolved
+);
+
+-- Index required by INFR-01: supports 30-day retention queries
+CREATE INDEX IF NOT EXISTS idx_alert_events_created_at
+    ON alert_events(created_at);
+
+-- Index for "active alerts" queries
+CREATE INDEX IF NOT EXISTS idx_alert_events_status
+    ON alert_events(status);
+
+-- Composite index for "active alerts per service" queries
+CREATE INDEX IF NOT EXISTS idx_alert_events_service_status
+    ON alert_events(service_name, status);
+
+-- Enable RLS (service role key bypasses RLS automatically — explicit policies added in Phase 3)
+ALTER TABLE alert_events ENABLE ROW LEVEL SECURITY;