Add self-hosted kids calendar app

Express + SQLite (node:sqlite, no native build step) family calendar:
parent accounts with household invites, per-child calendars with
save/duplicate/print, a token-gated read-only kiosk view for tablets,
and polling to keep parent and kiosk views in sync. Defaults to port 3007.

src/config.js

@@ -0,0 +1,12 @@
+const path = require('node:path');
+
+const DATA_DIR = process.env.DATA_DIR || path.join(__dirname, '..', 'data');
+
+module.exports = {
+  port: parseInt(process.env.PORT || '3007', 10),
+  dataDir: DATA_DIR,
+  dbPath: path.join(DATA_DIR, 'kids-calendar.sqlite'),
+  sessionSecret: process.env.SESSION_SECRET || 'dev-secret-change-me',
+  cookieSecure: process.env.COOKIE_SECURE === 'true',
+  disablePublicSignup: process.env.DISABLE_PUBLIC_SIGNUP === 'true',
+};