feat: merge cartsnitch/api into api/ subdirectory

Consolidate API gateway service into monorepo.
Squashed from https://github.com/cartsnitch/api main (89bacb1).

Co-Authored-By: Paperclip <noreply@paperclip.ing>

pyproject.toml

@@ -0,0 +1,58 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "cartsnitch-api"
+version = "0.1.0"
+description = "CartSnitch API Gateway — public-facing REST API"
+requires-python = ">=3.12"
+dependencies = [
+    "fastapi>=0.115.0",
+    "uvicorn[standard]>=0.30.0",
+    "pydantic[email]>=2.9.0",
+    "pydantic-settings>=2.5.0",
+    "sqlalchemy[asyncio]>=2.0.35",
+    "asyncpg>=0.30.0",
+    "alembic>=1.13,<2.0",
+    "psycopg2>=2.9,<3.0",
+    "python-jose[cryptography]>=3.3.0",
+    "passlib[bcrypt]>=1.7.4",
+    "httpx>=0.27.0",
+    "redis[hiredis]>=5.2.0",
+    "cryptography>=43.0.0",
+]
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=8.3.0",
+    "pytest-asyncio>=0.24.0",
+    "aiosqlite>=0.20.0",
+    "httpx>=0.27.0",
+    "ruff>=0.7.0",
+    "psycopg2-binary>=2.9,<3.0",
+]
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/cartsnitch_api"]
+
+[tool.pytest.ini_options]
+asyncio_mode = "auto"
+testpaths = ["tests"]
+
+[tool.ruff]
+target-version = "py312"
+line-length = 100
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "N", "UP", "B"]
+
+[tool.ruff.lint.per-file-ignores]
+"src/cartsnitch_api/**/routes*.py" = ["B008"]
+"src/cartsnitch_api/**/dependencies.py" = ["B008"]
+
+[tool.mypy]
+python_version = "3.12"
+ignore_missing_imports = true
+warn_return_any = true
+warn_unused_configs = true