feat: Add handler-base library for NATS AI/ML services

- Handler base class with graceful shutdown and signal handling
- NATSClient with JetStream and msgpack serialization
- Pydantic Settings for environment configuration
- HealthServer for Kubernetes probes
- OpenTelemetry telemetry setup
- Service clients: STT, TTS, LLM, Embeddings, Reranker, Milvus

pyproject.toml

@@ -0,0 +1,65 @@
+[project]
+name = "handler-base"
+version = "1.0.0"
+description = "Shared base library for AI/ML handler services"
+readme = "README.md"
+requires-python = ">=3.11"
+license = { text = "MIT" }
+authors = [{ name = "Davies Tech Labs" }]
+
+dependencies = [
+    # Async & messaging
+    "nats-py>=2.7.0",
+    "httpx>=0.27.0",
+    "msgpack>=1.0.0",
+    
+    # Data stores
+    "pymilvus>=2.4.0",
+    "redis>=5.0.0",
+    
+    # Observability
+    "opentelemetry-api>=1.20.0",
+    "opentelemetry-sdk>=1.20.0",
+    "opentelemetry-exporter-otlp-proto-grpc>=1.20.0",
+    "opentelemetry-exporter-otlp-proto-http>=1.20.0",
+    "opentelemetry-instrumentation-httpx>=0.44b0",
+    "opentelemetry-instrumentation-logging>=0.44b0",
+    
+    # MLflow
+    "mlflow>=2.10.0",
+    "psycopg2-binary>=2.9.0",
+    
+    # Utilities
+    "numpy>=1.26.0",
+    "pydantic>=2.5.0",
+    "pydantic-settings>=2.1.0",
+]
+
+[project.optional-dependencies]
+audio = [
+    "soundfile>=0.12.0",
+    "librosa>=0.10.0",
+    "webrtcvad>=2.0.10",
+]
+dev = [
+    "pytest>=8.0.0",
+    "pytest-asyncio>=0.23.0",
+    "ruff>=0.1.0",
+]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["handler_base"]
+
+[tool.ruff]
+line-length = 100
+target-version = "py311"
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "W"]
+
+[tool.pytest.ini_options]
+asyncio_mode = "auto"