[ECSoC_2026] security: Implement Modular Auth Session Manager, Input Sanitization & Password Strength Engine

[Babin123456]

Problem

Authentication scripts were fragmented across multiple single-purpose files (login-auth.js, signup-auth.js, account-auth.js), creating redundant boilerplate and lacking DOM XSS input sanitization and password strength scoring.

Current Behavior

User inputs in authentication forms were passed without sanitization, and password inputs lacked dynamic strength evaluation feedback.

Why This Improvement Is Needed

Centralizing authentication session logic and adding client-side input sanitization mitigates XSS security risks and enhances account security UX.

Proposed Solution

1. Create scripts/security-sanitizer.js providing HTML escaping, email sanitization, and password strength evaluation (0-4 scale).
2. Create scripts/auth-manager.js consolidating login, registration, profile state, and logout actions into a single session controller.
3. Update login.html, signup.html, account.html, and style.css.
4. Delete legacy single-purpose scripts (login-auth.js, signup-auth.js, account-auth.js) and Furnix-main/login.html.

Expected Outcome

• Unified authentication session management.
• Sanitized user input preventing XSS attacks.
• Dynamic password strength visualizer on registration form.

Additional Notes

Clean replacement of fragmented scripts with zero breaking changes.