feat: Phase 3 campaign management

Campaign CRUD API with cascading delete across all campaign-scoped
tables, a systems endpoint to seed the create-campaign form, active
campaign state wired to the sidebar chaos factor, and a campaign
management view for creating/switching/deleting campaigns.

server/routes/systems.js

@@ -0,0 +1,12 @@
+const express = require('express');
+const db = require('../db');
+
+const router = express.Router();
+
+const listSystems = db.prepare('SELECT * FROM systems ORDER BY name');
+
+router.get('/', (req, res) => {
+  res.json(listSystems.all());
+});
+
+module.exports = router;