feat: replace REST API with gRPC service

Complete migration from FastAPI/HTTP to gRPC:

Proto definition (proto/daena/v1/daena.proto):
- Daena service with 9 RPCs: GetStatus, GetHealth, GetConfig,
  ListPlugins, GetQueueState, ListPendingRecords, ListDeadRecords,
  ListSinks, ReloadConfig
- Messages for all request/response types with proper field types

gRPC server (src/daena/api/grpc_server.py):
- Async gRPC aio server with DaenaServicer implementation
- DaenaGRPCServer with start/stop/serve_forever lifecycle
- All endpoints delegate to DaenaRuntime

gRPC client (src/daena/cli/main.py):
- CLI now uses grpc.insecure_channel + DaenaStub
- Same commands: status, health, queue, sinks, plugins, config, version

Config changes:
- Remove FastAPI/uvicorn/http config, replace with grpc config
- GRPCConfig with host/port/max_workers

Dependency changes:
- Remove fastapi, uvicorn, starlette, anyio
- Add grpcio, grpcio-tools, protobuf
- Keep httpx for HTTP sink forwarding (separate from management API)

Tests:
- 8 new gRPC integration tests (test_grpc.py)
- All 31 tests passing, ruff clean

pyproject.toml

@@ -21,8 +21,9 @@ classifiers = [
 ]
 
 dependencies = [
-    "fastapi>=0.115",
-    "uvicorn[standard]>=0.30",
+    "grpcio>=1.70",
+    "grpcio-tools>=1.70",
+    "protobuf>=5.28",
     "pydantic>=2.0",
     "pydantic-settings>=2.0",
     "PyYAML>=6.0",