test: comprehensive integration tests for all API endpoints

Replace the existing integration test suite with a complete test covering
every registered API route. Tests use httptest with the real router and
a real DB connection (youpc.org mgmt schema).

Endpoint groups tested:
- Health, Auth (JWT validation, expired/invalid/wrong-secret)
- Current user (GET /api/me)
- Tenants (CRUD, auto-assign)
- Cases (CRUD with search/status filters)
- Parties (CRUD)
- Deadlines (CRUD, complete, batch create)
- Appointments (CRUD)
- Notes (CRUD)
- Dashboard
- Proceeding types & deadline rules
- Deadline calculator & determination (timeline, determine)
- Reports (cases, deadlines, workload, billing)
- Templates (CRUD, render)
- Time entries (CRUD, summary)
- Invoices (CRUD, status update)
- Billing rates (list, upsert)
- Notifications (list, unread count, mark read, preferences)
- Audit log (list, filtered)
- Case assignments (assign, unassign)
- Documents (list, meta)
- AI endpoints (availability check)
- Critical path E2E (case -> deadline -> appointment -> note -> time entry -> dashboard -> complete)

backend/seed/demo_data.sql

@@ -2,7 +2,7 @@
 -- Creates 1 test tenant, 5 cases with deadlines and appointments
 -- Run with: psql $DATABASE_URL -f demo_data.sql
 
-SET search_path TO mgmt, public;
+SET search_path TO kanzlai, public;
 
 -- Demo tenant
 INSERT INTO tenants (id, name, slug, settings) VALUES

backend/seed/seed_upc_timeline.sql

@@ -1,6 +1,6 @@
 -- UPC Proceeding Timeline: Full event tree with conditional deadlines
 -- Ported from youpc.org migrations 039 + 040
--- Run against mgmt schema in youpc.org Supabase instance
+-- Run against kanzlai schema in flexsiebels Supabase instance
 
 -- ========================================
 -- 1. Add is_spawn + spawn_label columns