feat(storage): add local fallback when Firebase is not configured

[aacritea]

Summary

This PR adds a local storage fallback to allow running the API without Firebase configuration.

Problem

Currently, the application crashes at startup if Firebase credentials are not configured:

google.auth.exceptions.DefaultCredentialsError

This prevents contributors from running the project locally.

Solution

• Added conditional Firebase initialization
• Implemented local storage fallback
• Introduced USE_LOCAL_STORAGE environment variable
• Prevented Firebase initialization during import

Changes

• Updated routes/video_routes.py
• Added USE_LOCAL_STORAGE support
• Improved storage initialization logic
• Updated .env.example

Testing

• Verified app runs without Firebase credentials
• Tested /hello endpoint locally
• Tested /test endpoint and confirmed external request handling

Local Testing Output

Application started successfully without Firebase credentials:

Starting the application
Running on http://localhost:5000

Tested /hello endpoint:

"GET /hello HTTP/1.1" 200 -

Tested /test endpoint:

Attempting to call test firebase function.
Failed to call firebase function: 404

Result

The project can now run locally without Firebase setup, improving developer onboarding.