Add icon support to Goal (Backend + Frontend + API + Tests)

[lohithdevulapally]

This PR introduces support for icons in the Goal feature across the full stack.

Backend:

• Added optional Icon field to Goal model
• Updated MongoDB integration

Frontend:

• Updated Goal type to include icon
• Displayed icon in GoalCard
• Integrated emoji picker in GoalManager

API:

• Added PUT request support for updating goals with icons

Testing:

• Added test coverage for GetGoalsForUser route

Result:
Users can now assign emoji icons to goals, and changes persist after refresh.

[gitguardian]

⚠️ GitGuardian has uncovered 2 secrets following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

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🔎 Detected hardcoded secrets in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
-	-	MongoDB Credentials	b204ae4	CommBank-Server/Secrets.json	View secret
-	-	MongoDB Credentials	b204ae4	CommBank-Server/appsettings.json	View secret

🛠 Guidelines to remediate hardcoded secrets

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To avoid such incidents in the future consider

• following these best practices for managing and storing secrets including API keys and other credentials
• install secret detection on pre-commit to catch secret before it leaves your machine and ease remediation.

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^{🦉 GitGuardian detects secrets in your source code to help developers and security teams secure the modern development process. You are seeing this because you or someone else with access to this repository has authorized GitGuardian to scan your pull request.}