feat: add Sustainability Goals Tracker dashboard

[Gunjan10-droid]

Related Issue

Closes #196

Description

Added a Sustainability Goals Tracker feature that allows users to create and monitor personal sustainability goals.

Features Added

• Added Sustainability Goals page

• Added navigation link from homepage

• Create custom sustainability goals

• Set target values and deadlines

• Track goal progress with progress bars

• Display completion percentage

• Achievement badge on goal completion

• Separate Active Goals and Completed Goals sections

• Dashboard summary showing:

  • Active Goals count
  • Completed Goals count
  • Completion Rate

• LocalStorage persistence for saved goals

Files Changed

• Frontend/index.html
• Frontend/style.css
• Frontend/sustainability.html
• Frontend/sustainability.js

Testing

• Created new goals successfully
• Added progress updates
• Verified goals move from Active to Completed
• Verified achievement badge display
• Verified dashboard statistics update correctly
• Verified data persists after page refresh

[Gunjan10-droid]

@thetechguardians could you label the pr for ssoc26?

[Vikrant0207]

@Gunjan10-droid resolve conflicts

[Gunjan10-droid]

@Gunjan10-droid resolve conflicts

@Vikrant0207 Done

[Gunjan10-droid]

@thetechguardians could you merge this pr?