Initial commit: Python SDK for Dragonchain (Prime)

Synchronous Python SDK modeled on prime-sdk-go. Provides DC1-HMAC-SHA256
auth, dataclass models, and resource clients for system, transaction,
transaction-type, smart-contract, and block endpoints, plus a YAML
credentials loader.

prime_sdk/system.py

@@ -0,0 +1,17 @@
+"""System endpoints (health, status)."""
+
+from .client import Client
+from .models import SystemStatus
+
+
+class SystemClient:
+    def __init__(self, client: Client):
+        self._client = client
+
+    def health(self) -> None:
+        """Check system health. Raises ``DragonchainAPIError`` if unhealthy."""
+        self._client.get("/api/v1/health")
+
+    def status(self) -> SystemStatus:
+        """Get system status."""
+        return self._client.get("/api/v1/status", SystemStatus)