Add roadmap management feature with database schema and user management

- Implemented roadmap.php for displaying and managing roadmap items with filters for quarter and status.
- Created schema.sql to define the database structure for users, invites, daily plans, tasks, brainstorm sessions, brainstorm cards, roadmap items, and integrations.
- Developed users.php for admin panel to manage team members and invitations, including functionality to create and revoke invites.

.env.example

@@ -0,0 +1,12 @@
+# MariaDB Verbinding
+DB_HOST="127.0.0.1"
+DB_PORT="3306"
+DB_NAME="fociz"
+DB_USER="root"
+DB_PASS="uw_wachtwoord"
+
+# Applicatie URL (voor uitnodigingslinks)
+APP_URL="https://uw-domein.nl"
+
+# Applicatie Geheime Sleutel (willekeurige tekenreeks)
+APP_SECRET="fociz-maria-db-super-secret-key-998877"