Remove password column from users table

Changes:
- Drop password column from users table (SSO authentication only)
- PULSE uses Authelia SSO, not password-based authentication
- Fixes 500 error: Field 'password' doesn't have a default value

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

server.js

@@ -46,7 +46,11 @@ async function initDatabase() {
       )
     `);
 
-    // Migrate existing users table to add missing columns
+    // Migrate existing users table to add missing columns and remove password column
+    try {
+      await connection.query(`ALTER TABLE users DROP COLUMN password`);
+      console.log('Removed password column (using SSO authentication)');
+    } catch (e) { /* Column doesn't exist */ }
     try {
       await connection.query(`ALTER TABLE users ADD COLUMN display_name VARCHAR(255) AFTER username`);
     } catch (e) { /* Column exists */ }