Add .db files to .gitignore and remove from tracking

.gitignore

@@ -1,4 +1,34 @@
 __pycache__/
 .venv/
 backend/.env
-backend/backend/static
+backend/backend/static
+
+# Database files - should not be in repo
+*.db
+*.db-journal
+*.db-wal
+backend/test.db
+data/test.db
+
+# Generated static files
+backend/static/*.png
+backend/static/*.pdf
+backend/static/*.jpg
+
+# Additional Python
+*.py[cod]
+*.so
+.Python
+*.egg-info/
+
+# Node
+node_modules/
+npm-debug.log*
+
+# IDE
+.vscode/
+.idea/
+.DS_Store
+
+# Logs
+*.log