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

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