db: Appwrite schema (isletmem db, 11 tables, indexes) + SDK helpers

- Created database 'isletmem' with 11 tables via Appwrite MCP:
  tenant_settings, customers, services, software, customer_software,
  calendar_events, tasks, finance_entries, invoices, invoice_items, audit_logs
- All tables use rowSecurity=true; row-level perms scoped to Appwrite Team (tenant)
- 18 indexes (composite on tenantId + queried columns; unique for invoice numbers, tenant_settings)
- src/lib/appwrite/schema.ts as TS source of truth (DATABASE_ID, TABLES, row types)
- src/lib/appwrite/client.ts (browser SDK)
- src/lib/appwrite/server.ts (node-appwrite admin + session clients)
- .env.example template, .env.local for dev (gitignored)
- typecheck script added

.gitignore

@@ -32,6 +32,7 @@ yarn-error.log*
 
 # env files (can opt-in for committing if needed)
 .env*
+!.env.example
 
 # vercel
 .vercel