Production hardening: security, resilience, observability, and compliance

Password complexity: custom validator requiring uppercase, lowercase, digit (min 8 chars)
Token expiry: 90-day token lifetime with refresh endpoint (60-90 day renewal window)
Health check: /api/health/ now pings Postgres + Redis, returns 503 on failure
Audit logging: async audit_log table for auth events (login, register, delete, etc.)
Circuit breaker: APNs/FCM push sends wrapped with 5-failure threshold, 30s recovery
FK indexes: 27 missing foreign key indexes across all tables (migration 017)
CSP header: default-src 'none'; frame-ancestors 'none'
Gzip compression: level 5 with media endpoint skipper
Prometheus metrics: /metrics endpoint using existing monitoring service
External timeouts: 15s push, 30s SMTP, context timeouts on all external calls

Migrations: 016 (token created_at), 017 (FK indexes), 018 (audit_log)
Tests: circuit breaker (15), audit service (8), token refresh (7), health (4),
       middleware expiry (5), validator (new)

migrations/017_fk_indexes.up.sql

@@ -0,0 +1,131 @@
+-- Migration: 017_fk_indexes
+-- Add indexes on all foreign key columns that are not already covered by existing indexes.
+-- Uses CREATE INDEX IF NOT EXISTS to be idempotent (safe to re-run).
+
+-- =====================================================
+-- auth / user tables
+-- =====================================================
+
+-- user_authtoken: user_id (unique FK, but ensure index exists)
+CREATE UNIQUE INDEX IF NOT EXISTS idx_authtoken_user_id
+    ON user_authtoken (user_id);
+
+-- user_userprofile: user_id (unique FK)
+CREATE UNIQUE INDEX IF NOT EXISTS idx_userprofile_user_id
+    ON user_userprofile (user_id);
+
+-- user_confirmationcode: user_id
+CREATE INDEX IF NOT EXISTS idx_confirmationcode_user_id
+    ON user_confirmationcode (user_id);
+
+-- user_passwordresetcode: user_id
+CREATE INDEX IF NOT EXISTS idx_passwordresetcode_user_id
+    ON user_passwordresetcode (user_id);
+
+-- user_applesocialauth: user_id (unique FK)
+CREATE UNIQUE INDEX IF NOT EXISTS idx_applesocialauth_user_id
+    ON user_applesocialauth (user_id);
+
+-- user_googlesocialauth: user_id (unique FK)
+CREATE UNIQUE INDEX IF NOT EXISTS idx_googlesocialauth_user_id
+    ON user_googlesocialauth (user_id);
+
+-- =====================================================
+-- push notification device tables
+-- =====================================================
+
+-- push_notifications_apnsdevice: user_id
+CREATE INDEX IF NOT EXISTS idx_apnsdevice_user_id
+    ON push_notifications_apnsdevice (user_id);
+
+-- push_notifications_gcmdevice: user_id
+CREATE INDEX IF NOT EXISTS idx_gcmdevice_user_id
+    ON push_notifications_gcmdevice (user_id);
+
+-- =====================================================
+-- notification tables
+-- =====================================================
+
+-- notifications_notificationpreference: user_id (unique FK)
+CREATE UNIQUE INDEX IF NOT EXISTS idx_notificationpreference_user_id
+    ON notifications_notificationpreference (user_id);
+
+-- =====================================================
+-- subscription tables
+-- =====================================================
+
+-- subscription_usersubscription: user_id (unique FK)
+CREATE UNIQUE INDEX IF NOT EXISTS idx_subscription_user_id
+    ON subscription_usersubscription (user_id);
+
+-- =====================================================
+-- residence tables
+-- =====================================================
+
+-- residence_residence: owner_id
+CREATE INDEX IF NOT EXISTS idx_residence_owner_id
+    ON residence_residence (owner_id);
+
+-- residence_residencesharecode: residence_id (may already exist from model index tag via GORM)
+CREATE INDEX IF NOT EXISTS idx_sharecode_residence_id
+    ON residence_residencesharecode (residence_id);
+
+-- residence_residencesharecode: created_by_id
+CREATE INDEX IF NOT EXISTS idx_sharecode_created_by_id
+    ON residence_residencesharecode (created_by_id);
+
+-- =====================================================
+-- task tables
+-- =====================================================
+
+-- task_task: created_by_id
+CREATE INDEX IF NOT EXISTS idx_task_created_by_id
+    ON task_task (created_by_id);
+
+-- task_task: assigned_to_id
+CREATE INDEX IF NOT EXISTS idx_task_assigned_to_id
+    ON task_task (assigned_to_id);
+
+-- task_task: category_id
+CREATE INDEX IF NOT EXISTS idx_task_category_id
+    ON task_task (category_id);
+
+-- task_task: priority_id
+CREATE INDEX IF NOT EXISTS idx_task_priority_id
+    ON task_task (priority_id);
+
+-- task_task: frequency_id
+CREATE INDEX IF NOT EXISTS idx_task_frequency_id
+    ON task_task (frequency_id);
+
+-- task_task: contractor_id
+CREATE INDEX IF NOT EXISTS idx_task_contractor_id
+    ON task_task (contractor_id);
+
+-- task_task: parent_task_id
+CREATE INDEX IF NOT EXISTS idx_task_parent_task_id
+    ON task_task (parent_task_id);
+
+-- task_taskcompletionimage: completion_id
+CREATE INDEX IF NOT EXISTS idx_completionimage_completion_id
+    ON task_taskcompletionimage (completion_id);
+
+-- task_document: created_by_id
+CREATE INDEX IF NOT EXISTS idx_document_created_by_id
+    ON task_document (created_by_id);
+
+-- task_document: task_id
+CREATE INDEX IF NOT EXISTS idx_document_task_id
+    ON task_document (task_id);
+
+-- task_documentimage: document_id
+CREATE INDEX IF NOT EXISTS idx_documentimage_document_id
+    ON task_documentimage (document_id);
+
+-- task_contractor: residence_id
+CREATE INDEX IF NOT EXISTS idx_contractor_residence_id
+    ON task_contractor (residence_id);
+
+-- task_reminderlog: notification_id
+CREATE INDEX IF NOT EXISTS idx_reminderlog_notification_id
+    ON task_reminderlog (notification_id);