Add admin panel, WebSocket support, and API versioning

Introduce an admin portal (React + Nginx), WebSocket routing, and
API versioning middleware with `/api/v1/` prefix deprecation.
Add master API key authentication, new Prometheus metrics for AI
token consumption and active WebSockets, and extend S3 config
with a public endpoint URL. Update test paths and fixtures to
align with the new routing structure.

sdk/imago_client/__init__.py

@@ -0,0 +1,40 @@
+"""
+Imago Client SDK for Python.
+
+A modern, async Python client for the Imago backend.
+"""
+
+from .client import HubClient
+from .exceptions import (
+    ImagoError,
+    AuthError,
+    QuotaError,
+    NotFoundError,
+    APIError,
+    PipelineError,
+)
+from .models import (
+    HubImage,
+    ExifData,
+    OcrData,
+    AiData,
+    ProcessingInfo,
+)
+from .websocket import PipelineStream, AdminMonitorStream
+
+__all__ = [
+    "HubClient",
+    "ImagoError",
+    "AuthError",
+    "QuotaError",
+    "NotFoundError",
+    "APIError",
+    "PipelineError",
+    "HubImage",
+    "ExifData",
+    "OcrData",
+    "AiData",
+    "ProcessingInfo",
+    "PipelineStream",
+    "AdminMonitorStream",
+]