build: switch to uv, hatchling and ruff-only tooling

.gitignore

@@ -52,10 +52,11 @@ htmlcov/
 
 # Environment variables
 .env
+!.env.example
 .env.local
 .env.backup-*
 
-# API keys
+# Keys
 keys/
 *.key
 
@@ -72,3 +73,7 @@ Thumbs.db
 
 # Audit logs (development only - production should use volumes)
 audit.log
+
+# Local state
+.data/
+coverage.xml