chore: initial project scaffold

Set up IdeaForge project structure with documentation, architecture spec,
and development guidelines for both backend (Python) and frontend (Flutter).

.gitignore

@@ -0,0 +1,69 @@
+# python
+__pycache__/
+*.py[cod]
+*$py.class
+*.egg-info/
+*.egg
+dist/
+build/
+.eggs/
+*.whl
+
+# virtual environments
+.venv/
+venv/
+ENV/
+
+# uv
+uv.lock
+
+# database
+*.db
+*.sqlite3
+data/
+
+# testing
+.coverage
+htmlcov/
+.pytest_cache/
+coverage.xml
+
+# mypy
+.mypy_cache/
+
+# ruff
+.ruff_cache/
+
+# environment
+.env
+.env.local
+
+# flutter
+frontend/.dart_tool/
+frontend/.packages
+frontend/.pub-cache/
+frontend/.pub/
+frontend/build/
+frontend/.flutter-plugins
+frontend/.flutter-plugins-dependencies
+
+# code generation
+frontend/**/*.g.dart
+frontend/**/*.freezed.dart
+
+# editor
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# os
+.DS_Store
+Thumbs.db
+
+# docker
+*.log
+
+# evaluation batches (local data)
+evaluation_batches/