Fix global installation by adding proper Python packaging

- Add build-system configuration to pyproject.toml
- Add project metadata with dependencies from requirements.txt
- Add entry point: rag-mini = mini_rag.cli:cli
- Enable proper pip install -e . workflow

Fixes broken global rag-mini command that failed due to hardcoded bash script paths.
Users can now install globally with pip and use rag-mini from any directory.

pyproject.toml

@@ -31,4 +31,31 @@ extend-exclude = '''
   | build
   | dist
 )/
-'''
+'''
+
+[build-system]
+requires = ["setuptools>=61.0"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "mini-rag"
+version = "2.1.0"
+dependencies = [
+    "lancedb>=0.5.0",
+    "pandas>=2.0.0",
+    "numpy>=1.24.0",
+    "pyarrow>=14.0.0",
+    "watchdog>=3.0.0",
+    "requests>=2.28.0",
+    "click>=8.1.0",
+    "rich>=13.0.0",
+    "PyYAML>=6.0.0",
+    "rank-bm25>=0.2.2",
+    "psutil"
+]
+
+[project.scripts]
+rag-mini = "mini_rag.cli:cli"
+
+[tool.setuptools]
+packages = ["mini_rag"]