feat(saas): add down migrations for all incremental schema changes (AUD3-DB-01)

- 16 down SQL files in migrations/down/ for each incremental migration
- db::run_down_migrations() executes rollback files in reverse order
- migrate_down CLI task: task=migrate_down timestamp=20260402
- Initial schema and seed data excluded (would be destructive)

crates/zclaw-saas/migrations/down/20260330000001_scheduled_tasks.sql

@@ -0,0 +1,2 @@
+-- Down: Drop scheduled_tasks table
+DROP TABLE IF EXISTS scheduled_tasks;

crates/zclaw-saas/migrations/down/20260331000001_accounts_llm_routing.sql

@@ -0,0 +1,2 @@
+-- Down: Remove llm_routing column from accounts
+ALTER TABLE accounts DROP COLUMN IF EXISTS llm_routing;

crates/zclaw-saas/migrations/down/20260331000002_agent_templates_extensions.sql

@@ -0,0 +1,11 @@
+-- Down: Remove extension columns from agent_templates
+DROP INDEX IF EXISTS idx_agent_templates_source_id;
+ALTER TABLE agent_templates DROP COLUMN IF EXISTS source_id;
+ALTER TABLE agent_templates DROP COLUMN IF EXISTS version;
+ALTER TABLE agent_templates DROP COLUMN IF EXISTS emoji;
+ALTER TABLE agent_templates DROP COLUMN IF EXISTS communication_style;
+ALTER TABLE agent_templates DROP COLUMN IF EXISTS personality;
+ALTER TABLE agent_templates DROP COLUMN IF EXISTS quick_commands;
+ALTER TABLE agent_templates DROP COLUMN IF EXISTS welcome_message;
+ALTER TABLE agent_templates DROP COLUMN IF EXISTS scenarios;
+ALTER TABLE agent_templates DROP COLUMN IF EXISTS soul_content;

crates/zclaw-saas/migrations/down/20260401000001_provider_keys_last_used.sql

@@ -0,0 +1,2 @@
+-- Down: Remove last_used_at from provider_keys
+ALTER TABLE provider_keys DROP COLUMN IF EXISTS last_used_at;

crates/zclaw-saas/migrations/down/20260401000002_remove_quota_reset_interval.sql

@@ -0,0 +1,2 @@
+-- Down: Re-add quota_reset_interval to provider_keys
+ALTER TABLE provider_keys ADD COLUMN IF NOT EXISTS quota_reset_interval TEXT;

crates/zclaw-saas/migrations/down/20260401000003_models_is_embedding.sql

@@ -0,0 +1,5 @@
+-- Down: Remove is_embedding and model_type from models
+DROP INDEX IF EXISTS idx_models_model_type;
+DROP INDEX IF EXISTS idx_models_is_embedding;
+ALTER TABLE models DROP COLUMN IF EXISTS model_type;
+ALTER TABLE models DROP COLUMN IF EXISTS is_embedding;

crates/zclaw-saas/migrations/down/20260401000004_accounts_password_version.sql

@@ -0,0 +1,4 @@
+-- Down: Remove password security columns from accounts
+ALTER TABLE accounts DROP COLUMN IF EXISTS locked_until;
+ALTER TABLE accounts DROP COLUMN IF EXISTS failed_login_count;
+ALTER TABLE accounts DROP COLUMN IF EXISTS password_version;

crates/zclaw-saas/migrations/down/20260401000005_rate_limit_events.sql

@@ -0,0 +1,2 @@
+-- Down: Drop rate_limit_events table
+DROP TABLE IF EXISTS rate_limit_events;

crates/zclaw-saas/migrations/down/20260402000001_billing_tables.sql

@@ -0,0 +1,6 @@
+-- Down: Drop billing tables (reverse creation order due to FK)
+DROP TABLE IF EXISTS billing_usage_quotas;
+DROP TABLE IF EXISTS billing_payments;
+DROP TABLE IF EXISTS billing_invoices;
+DROP TABLE IF EXISTS billing_subscriptions;
+DROP TABLE IF EXISTS billing_plans;

crates/zclaw-saas/migrations/down/20260402000002_knowledge_base.sql

@@ -0,0 +1,7 @@
+-- Down: Drop knowledge base tables (reverse creation order due to FK)
+-- Note: This does NOT reverse the pgvector extension installation or role permission updates.
+DROP TABLE IF EXISTS knowledge_usage;
+DROP TABLE IF EXISTS knowledge_versions;
+DROP TABLE IF EXISTS knowledge_chunks;
+DROP TABLE IF EXISTS knowledge_items;
+DROP TABLE IF EXISTS knowledge_categories;

crates/zclaw-saas/migrations/down/20260402000003_scheduled_task_results.sql

@@ -0,0 +1,3 @@
+-- Down: Remove result columns from scheduled_tasks
+ALTER TABLE scheduled_tasks DROP COLUMN IF EXISTS last_duration_ms;
+ALTER TABLE scheduled_tasks DROP COLUMN IF EXISTS last_result;

crates/zclaw-saas/migrations/down/20260403000001_accounts_template_assignment.sql

@@ -0,0 +1,2 @@
+-- Down: Remove assigned_template_id from accounts
+ALTER TABLE accounts DROP COLUMN IF EXISTS assigned_template_id;

crates/zclaw-saas/migrations/down/20260403000002_webhooks.sql

@@ -0,0 +1,3 @@
+-- Down: Drop webhook tables (reverse creation order due to FK)
+DROP TABLE IF EXISTS webhook_deliveries;
+DROP TABLE IF EXISTS webhook_subscriptions;

crates/zclaw-saas/migrations/down/20260404000001_model_groups.sql

@@ -0,0 +1,3 @@
+-- Down: Drop model group tables (reverse creation order due to FK)
+DROP TABLE IF EXISTS model_group_members;
+DROP TABLE IF EXISTS model_groups;

crates/zclaw-saas/migrations/down/20260405000001_industry_agent_templates.sql

@@ -0,0 +1,6 @@
+-- Down: Remove industry agent template seed data
+DELETE FROM agent_templates WHERE id IN (
+    'edu-teacher-001',
+    'healthcare-admin-001',
+    'design-shantou-001'
+);