feat: initial project scaffold

pyproject.toml (Python 3.12, uv), codex/ package (config, db, models),
infra/ (docker-compose + schema), .env.example, .gitignore, README.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -0,0 +1,46 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "codex"
+version = "0.1.0"
+description = "Personal knowledge base for scientific papers — provenance, citation graph, semantic search."
+readme = "README.md"
+requires-python = ">=3.12"
+dependencies = [
+    "psycopg[binary]>=3.1",
+    "pgvector>=0.3",
+    "pydantic-settings>=2",
+    "sentence-transformers>=3",
+    "typer>=0.12",
+    "httpx>=0.27",
+    "tenacity>=8",
+]
+
+[project.scripts]
+codex = "codex.cli:app"
+
+[dependency-groups]
+dev = [
+    "ruff>=0.4",
+    "mypy>=1.10",
+    "pytest>=8",
+    "pytest-mock>=3",
+]
+
+[tool.ruff]
+target-version = "py312"
+line-length = 100
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "UP", "B", "SIM"]
+ignore = []
+
+[tool.mypy]
+python_version = "3.12"
+strict = true
+ignore_missing_imports = true
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]