Make Railway root deploy compatible for nested FastAPI app

[Copilot]

Railway build was failing because deployment config lived under Google hackthon Selling Agent/ while Railway resolves build/start config from repository root. This PR adds root-level deploy config and updates startup/module imports so the app can boot from root without breaking the existing subdirectory layout.

• Root-level Railway config (non-breaking)

  • Added at repo root:
    • Procfile
    • requirements.txt
    • runtime.txt (python-3.13)
    • nixpacks.toml
  • Kept original copies in Google hackthon Selling Agent/ for backward compatibility.

• Root startup path alignment

  • Updated root Procfile to point to the nested module:

    web: uvicorn "Google hackthon Selling Agent.app.main:app" --host 0.0.0.0 --port $PORT

  • Aligned root nixpacks.toml start command to the same module path.

• Import-path hardening for root execution

  • Switched absolute from app... imports to package-relative imports in:
    • Google hackthon Selling Agent/app/main.py
    • Google hackthon Selling Agent/app/routes/analytics.py
    • Google hackthon Selling Agent/app/routes/vendors.py
    • Google hackthon Selling Agent/app/routes/group_orders.py
  • This preserves subdirectory execution while enabling root-based module resolution.

• Representative code change

  # before
  from app.database import db
  from app.routes import vendors, analytics, group_orders, chat
  
  # after
  from .database import db
  from .routes import vendors, analytics, group_orders, chat