fix(auth): increase default token expiration from 30m to 8h

Short-lived tokens caused frequent "Could not validate credentials"
errors in Swagger UI despite persistAuthorization keeping stale tokens.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pythoninthegrass

app/main.py

@@ -65,7 +65,7 @@
 PORT = config("PORT", default=3000, cast=int)
 SECRET_KEY = config("SECRET_KEY")
 ALGORITHM = config("ALGORITHM", default="HS256")
-TOKEN_EXPIRE = config("TOKEN_EXPIRE", default=30, cast=int)
+TOKEN_EXPIRE = config("TOKEN_EXPIRE", default=480, cast=int)
 
 try:
     DB_USER = config("DB_USER")