Initial commit: Maskan CRM backend

Independent FastAPI backend for Maskan CRM.

Owns contacts, organizations, leads, pipelines, activities, products,
quotes, users, permissions, audit records and first-party integration
credentials, with Alembic migrations against PostgreSQL.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitignore

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+.venv/
+.venv311/
+venv/
+__pycache__/
+*.py[cod]
+*.egg-info/
+.pytest_cache/
+.ruff_cache/
+.mypy_cache/
+.coverage
+htmlcov/
+dist/
+build/
+
+node_modules/
+
+.env
+.env.*
+!.env.example
+!.env.local.example
+!.env.development.example
+!.env.testing.example
+!.env.production.example
+
+*.db
+*.sqlite
+*.sqlite3
+*.log
+
+.DS_Store
+.idea/
+.vscode/