Issue 23: Python SDK Core Client

[laraibg786]

Goal

Build a Python SDK package (permit-sdk) providing a typed API wrapper for the permit backend, with built-in retries, timeout handling, and error mapping. Customers import permit_sdk and call activate() and get_status() without managing HTTP details.

Requirements

Functional

• PermitClient(api_key, api_url) initialization.
• client.activate(license_key, device_fingerprint) → returns session token and policy snapshot.
• client.get_status(session_token) → returns status enum (ACTIVE, GRACE, EXPIRED, REVOKED).
• Retry on HTTP 5xx or timeout: up to 3 retries with exponential backoff (100ms, 200ms, 400ms).
• Map API error codes to typed exceptions: ActivationError, SessionExpiredError, LicenseRevokedError.

Technical

• Python: 3.11+.
• Dependencies: httpx, pydantic.
• Auth: API key in header Authorization: ApiKey {api_key}.
• Timeout: 30 seconds per request.
• Async: httpx.AsyncClient for async variant (activate_async()).
• Package: PyPI-ready structure under sdk/.

Acceptance Criteria

• activate() returns session token on success.
• activate() raises ActivationError on 4xx.
• Retries 3 times on 5xx before raising.
• Async variant works with await client.activate_async(...).

Dependencies

• Blocked by: Issue 06: JWT Authentication #6, Issue 11: Create License Endpoint #11, Issue 17: Activation Eligibility Validation #17, Issue 18: Activation Session Creation and Device Binding #18.
• Blocks: Issue 24: SDK Heartbeat Loop and State Machine #24, Issue 25: SDK Test Suite #25, Issue 27: SDK Demo Application #27.