Switch to uv as dependency manager

- Add pyproject.toml with project metadata and pinned dependency ranges
- Add uv.lock (generated by `uv lock`) for reproducible installs
- Add .python-version pinning Python 3.11
- Remove requirements.txt (superseded by pyproject.toml)

Install: `uv sync`
Run: `uv run python main.py`

https://claude.ai/code/session_01HaUFs7SaLD5SoiuGCY27Tw

pyproject.toml

@@ -0,0 +1,31 @@
+[project]
+name = "meister-eder"
+version = "0.1.0"
+description = "AI-powered conversational registration agent for Spielgruppe Pumuckl"
+requires-python = ">=3.11"
+dependencies = [
+    # At least one AI provider SDK is required; both are included so the
+    # operator can choose at runtime via the AI_PROVIDER env variable.
+    "anthropic>=0.40.0",
+    "openai>=1.50.0",
+    # Configuration
+    "python-dotenv>=1.0.0",
+    # Registration schema validation
+    "jsonschema>=4.23.0",
+]
+
+[project.scripts]
+meister-eder = "main:main"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src"]
+
+[tool.uv]
+dev-dependencies = [
+    "pytest>=8.0.0",
+    "pytest-mock>=3.14.0",
+]