feat: add FastAPI backend with PostgreSQL and start script fixes

- Add server/ directory with FastAPI backend
- Fix server/start.sh to properly handle venv on Windows/Git Bash
- Add alembic migrations and pyproject.toml
- Add server tests

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

server/src/x_financial_server.egg-info/SOURCES.txt

@@ -0,0 +1,41 @@
+README.md
+pyproject.toml
+src/app/__init__.py
+src/app/main.py
+src/app/api/__init__.py
+src/app/api/deps.py
+src/app/api/router.py
+src/app/api/v1/__init__.py
+src/app/api/v1/router.py
+src/app/api/v1/endpoints/__init__.py
+src/app/api/v1/endpoints/bootstrap.py
+src/app/api/v1/endpoints/employees.py
+src/app/api/v1/endpoints/health.py
+src/app/api/v1/endpoints/reimbursements.py
+src/app/core/__init__.py
+src/app/core/bootstrap.py
+src/app/core/config.py
+src/app/db/__init__.py
+src/app/db/base.py
+src/app/db/base_class.py
+src/app/db/session.py
+src/app/models/__init__.py
+src/app/models/approval.py
+src/app/models/employee.py
+src/app/models/reimbursement.py
+src/app/repositories/__init__.py
+src/app/repositories/employee.py
+src/app/repositories/reimbursement.py
+src/app/schemas/__init__.py
+src/app/schemas/bootstrap.py
+src/app/schemas/employee.py
+src/app/schemas/reimbursement.py
+src/app/services/__init__.py
+src/app/services/employee.py
+src/app/services/reimbursement.py
+src/x_financial_server.egg-info/PKG-INFO
+src/x_financial_server.egg-info/SOURCES.txt
+src/x_financial_server.egg-info/dependency_links.txt
+src/x_financial_server.egg-info/requires.txt
+src/x_financial_server.egg-info/top_level.txt
+tests/test_imports.py