Add password reset functionality and SMTP mailer class

- Implemented reset-password.php for users to reset their passwords securely.
- Added validation for reset tokens and password strength checks.
- Created mailer.php to handle sending emails via SMTP, including password reset and invitation emails.
- Integrated responsive HTML email templates for better user experience.

config/schema.sql

@@ -31,6 +31,17 @@ CREATE TABLE IF NOT EXISTS `invites` (
   CONSTRAINT `fk_invites_user` FOREIGN KEY (`created_by_id`) REFERENCES `users` (`id`) ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
 
+CREATE TABLE IF NOT EXISTS `password_resets` (
+  `id` INT AUTO_INCREMENT PRIMARY KEY,
+  `email` VARCHAR(191) NOT NULL,
+  `token` VARCHAR(64) NOT NULL UNIQUE,
+  `expires_at` DATETIME NOT NULL,
+  `used_at` DATETIME NULL,
+  `created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  INDEX (`email`),
+  INDEX (`token`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
 CREATE TABLE IF NOT EXISTS `daily_plans` (
   `id` INT AUTO_INCREMENT PRIMARY KEY,
   `user_id` INT NOT NULL,