fix(auth): enforce password complexity and remove debug logs

[Prateek2007-cmd]

Description

Closes #2247
This PR resolves security and code hygiene technical debt in the user registration flow:

1. Unenforced Password Complexity: Previously, only a minimum length of 8 characters was required for passwords. This PR implements a strict regex-based complexity check that requires at least one uppercase letter, one lowercase letter, one number, and one special character, resolving the related TODO.
2. Production Debug Logs: Removed lingering console.log statements from register.js that clutter the production console and could inadvertently leak execution context.

Changes Made

• Added complexityRegex to register.js to validate the password against industry-standard complexity rules.
• Added specific UI error messaging to messageBox to alert the user if the complexity requirements are not met.
• Removed console.log("register.js loaded"); and console.log("Success:", data);.
• Removed the obsolete // TODO: Prevent signup triggers if password complexity score is poor comment.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• Security patch

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