Add advanced projects and fix starter code downloads

[jaygaikar-09]

Summary [required]

This PR adds two new Advanced-level projects to the DevPath learning catalog and fixes starter-code serving for nested paths. The new projects include fully runnable starter templates for a real-time chat application and a JWT authentication REST API. In addition, starter file download/view logic was improved to correctly resolve nested directories safely, and new tests/documentation were added to cover the updated behavior.

Related Issue [required]

Closes #92

Type of Change [required]

• Bug fix — resolves a broken behaviour
• Feature — adds new functionality
• Data — adds new projects to data/projects.json
• Documentation — updates docs, README, or code comments only
• Style — CSS or visual changes only, no logic change
• Refactor — restructures code without changing behaviour
• Test — adds or updates tests

What Was Changed [required]

File	Change made
data/projects.json	Added Advanced-level projects (id 8 and id 9) with full metadata
starter_code/realtime_chat/app.py	Added working Flask-SocketIO chat server
starter_code/realtime_chat/templates/chat.html	Added realtime chat frontend using Socket.IO
starter_code/realtime_chat/requirements.txt	Added dependencies for realtime chat starter
starter_code/jwt_auth_api.py	Added JWT authentication API starter implementation
starter_code/jwt_requirements.txt	Added JWT starter dependencies
utils/file_server.py	Fixed nested starter file path resolution and added safe path handling
routes/main_routes.py	Updated download routes to support nested starter files
tests/test_basic.py	Added tests for project 8 & 9 code/download endpoints
SECURITY.md	Updated documentation for secure path handling
docs/architecture.md	Updated architecture docs for starter serving logic

How to Test This PR [required]

1. Clone the repository
2. Checkout the branch:

   git checkout add-advanced-projects-clean

[vercel]

@jaygaikar-09 is attempting to deploy a commit to the komalsony234-1530's projects Team on Vercel.

A member of the Team first needs to authorize it.

[komalharshita]

@jaygaikar-09 kindly resolve the merge conflicts

[jaygaikar-09]

@komalharshita Done!

[komalharshita]

Thanks for the contribution.

This PR contains some valuable improvements, particularly the nested starter-code path resolution, download handling fixes, additional tests, and documentation updates.

However, before merge there are several concerns that should be addressed.

Main issues:

• The PR combines two separate objectives:

• fixing starter-code download/path handling
• adding multiple new Advanced projects and starter templates

This significantly increases review scope and makes validation harder. Please consider separating bug-fix work from large catalog/content additions where possible.

• The new starter projects contain educational implementations that rely on in-memory storage and development-oriented defaults. Please clearly document these limitations so contributors and learners do not mistake them for production-ready patterns.

• Since the primary logic change is path resolution and security validation, additional tests should be added for:

• path traversal attempts (../)
• invalid nested paths
• malformed starter_code values
• absolute-path rejection

• Please perform a final consistency review of the newly added project metadata, roadmap structure, and resource links.

Once these concerns are addressed, the PR can be reviewed again.

[komalharshita]

Closing this PR for inactivity. Please open a fresh PR if possible.