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/block.py

@@ -0,0 +1,12 @@
+"""Block endpoints."""
+
+from .client import Client
+from .models import Block
+
+
+class BlockClient:
+    def __init__(self, client: Client):
+        self._client = client
+
+    def get(self, block_id: str) -> Block:
+        return self._client.get(f"/api/v1/block/{block_id}", Block)