fix: Apply dark mode styling to login and signup pages

[Copilot]

1. Title

fix: Apply dark mode styling to login and signup pages

2. Description

Dark mode toggle was partially implemented but several UI elements retained light mode colors, breaking readability. Welcome message box, form links, and terms checkbox container remained white with dark text in dark mode.

3. Related Issues

Fixes #issue_number_here

4. Changes Made

Added 8 CSS rules to src/pages/login.html targeting dark mode elements:

• .message - Welcome box background → #101927
• .title, .subtitle, .brand - Text colors → blue/gray palette
• .terms-checkbox-container - Checkbox container background → #0f172a
• .form-link span, .form-link a - Link text visibility → light colors
• header - Form header color → #60a5fa

body.dark-theme .message{ background:#101927; color:#e6e6f0; border:1px solid #1f2a3a; }
body.dark-theme .terms-checkbox-container{ background:#0f172a; border:1px solid #334155; }
body.dark-theme .form-link span{ color:#cbd5e1; }

5. Checklist

• I have read the project's contributing guidelines.
• My code follows the project's coding style and conventions.
• I have performed a thorough self-review of my own code.
• I have added comments to my code, especially in complex or non-obvious sections.
• I have made corresponding updates to the documentation (e.g., README, API docs) if my changes require it.
• My changes introduce no new warnings or errors during compilation/runtime.
• I have added new tests or updated existing ones to cover my changes, and they pass locally.
• Any dependent changes (e.g., API updates, library versions) have been addressed.

6. Screenshots/GIFs

Login Page:

Before	After

Signup Page:

Before	After

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Dark mode styling properly in login and sign up page.</issue_title>
<issue_description>### Describe the bug

Dark mode styling is not properly applied on the Login and Sign Up pages. Some UI elements retain light mode colors, causing inconsistent appearance and poor readability.

To Reproduce

Open the application in the browser.

Switch the theme to Dark Mode (via toggle or system setting).

Navigate to the Login Page (/login).

Observe background, text, and button colors.

Repeat for Sign Up Page (/signup).

Expected behavior

All UI elements (background, text, input fields, buttons, and labels) should adapt to the dark theme — maintaining readability and visual consistency.

Additional context

https://github.com/user-attachments/assets/b869d46a-2759-4441-bf0e-a32531c4f5b2</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Dark mode styling properly in login and sign up page. #1055

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