Create API module structure

[wklumpen]

Description

Set up new api/ module in SPUR repo to provide HTTP API wrapper around the simulation engine.

Tasks

• Create spur/api/ directory
• Create __init__.py, server.py, session.py, schemas.py
• Update main spur/__init__.py to expose api if installed
• Add Flask to optional dependencies in setup.py with [api] extra
• Test that pip install -e .[api] installs Flask dependencies

Acceptance Criteria

• Can import from spur.api import create_app
• Module structure matches design
• pip install spur-sim[api] installs Flask dependencies
• Import works even without Flask installed (graceful fail)

Time Estimate

1 hour

Dependencies

None

Files Changed

• spur/api/__init__.py (new)
• spur/api/server.py (new)
• spur/api/session.py (new)
• spur/api/schemas.py (new)
• spur/__init__.py (modified)
• setup.py (modified)