update local startup flow and add root env example

Make the project start more reliably in the current Windows bash setup, add a safe root .env.example for onboarding, and lower the backend Python floor to 3.11 to match the validated local environment.

backend/pyproject.toml

@@ -3,7 +3,7 @@ name = "jarvis-backend"
 version = "0.1.0"
 description = "Jarvis Personal AI Assistant - Backend"
 readme = "README.md"
-requires-python = ">=3.12"
+requires-python = ">=3.11"
 license = { text = "MIT" }
 
 dependencies = [
@@ -72,7 +72,7 @@ build-backend = "hatchling.build"
 packages = ["app"]
 
 [tool.ruff]
-target-version = "py312"
+target-version = "py311"
 line-length = 100
 select = ["E", "F", "I", "N", "W", "UP"]