Refactor: Move backend files to backend/ directory and split .gitignore

backend/pyproject.toml

@@ -0,0 +1,47 @@
+[project]
+name = "ea-chatbot"
+version = "0.1.0"
+description = "An election analytics chatbot using LangGraph."
+requires-python = ">=3.13"
+dependencies = [
+    "langgraph",
+    "langchain",
+    "langchain-openai",
+    "langchain-google-genai",
+    "langchain-community",
+    "pandas",
+    "matplotlib",
+    "psycopg2-binary",
+    "psycopg[binary]>=3.1.0",
+    "termcolor>=3.3.0",
+    "sqlalchemy>=2.0.46",
+    "pyyaml>=6.0.3",
+    "streamlit>=1.54.0",
+    "rich>=14.3.2",
+    "alembic>=1.13.0",
+    "authlib>=1.3.0",
+    "httpx>=0.27.0",
+    "argon2-cffi>=23.1.0",
+    "email-validator>=2.1.0",
+    "fastapi>=0.109.0",
+    "uvicorn>=0.27.0",
+    "python-jose[cryptography]>=3.3.0",
+    "python-multipart>=0.0.9",
+    "langgraph-checkpoint-postgres>=2.0.0",
+]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/ea_chatbot"]
+
+[dependency-groups]
+dev = [
+    "pytest>=9.0.2",
+    "pytest-cov>=7.0.0",
+    "pytest-asyncio>=0.23.0",
+    "ruff>=0.9.3",
+    "mypy>=1.14.1",
+]