Scaffold backend (FastAPI/uv) and frontend (SvelteKit/bun)

Backend: FastAPI app with health check, AppError hierarchy, stderr
logging via LOG_LEVEL, ruff+pyright(strict) config, pytest passing.

Frontend: SvelteKit (TS) with prettier, eslint, vitest (unit +
component), adapter-node for self-hosted deployment on Zeus.

Co-Authored-By: Claude <noreply@anthropic.com>

backend/pyproject.toml

@@ -0,0 +1,50 @@
+[project]
+name = "sagaphone-backend"
+version = "0.1.0"
+description = "Sagaphone backend — family-tree simulation, narration, and TTS streaming API."
+readme = "README.md"
+requires-python = ">=3.12"
+dependencies = [
+    "fastapi>=0.115",
+    "uvicorn[standard]>=0.32",
+    "anthropic>=0.40",
+]
+
+[dependency-groups]
+dev = [
+    "ruff>=0.8",
+    "pyright>=1.1.390",
+    "pytest>=8.3",
+    "pytest-asyncio>=0.24",
+    "httpx>=0.27",
+]
+
+[tool.ruff]
+line-length = 100
+target-version = "py312"
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "UP", "B", "SIM"]
+
+[tool.pyright]
+include = ["app", "tests"]
+typeCheckingMode = "strict"
+pythonVersion = "3.12"
+
+[[tool.pyright.executionEnvironments]]
+root = "tests"
+reportUnknownMemberType = false
+reportUnknownVariableType = false
+reportUnknownParameterType = false
+reportMissingParameterType = false
+reportMissingTypeStubs = false
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["app"]