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/app/api/__init__.py

@@ -0,0 +1 @@
+__all__ = ["router"]

server/src/app/api/deps.py

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+from collections.abc import Generator
+
+from sqlalchemy.orm import Session
+
+from app.db.session import get_session_factory
+
+
+def get_db() -> Generator[Session, None, None]:
+    db = get_session_factory()()
+    try:
+        yield db
+    finally:
+        db.close()

server/src/app/api/router.py

@@ -0,0 +1,6 @@
+from fastapi import APIRouter
+
+from app.api.v1.router import router as v1_router
+
+api_router = APIRouter()
+api_router.include_router(v1_router)

server/src/app/api/v1/__init__.py

@@ -0,0 +1 @@
+__all__ = ["router"]

server/src/app/api/v1/endpoints/__init__.py

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+__all__ = ["health", "employees", "reimbursements"]

server/src/app/api/v1/endpoints/bootstrap.py

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+from __future__ import annotations
+
+from fastapi import APIRouter, status
+
+from app.core.bootstrap import build_bootstrap_state, persist_bootstrap_config
+from app.core.config import get_settings
+from app.schemas.bootstrap import BootstrapSetupPayload, BootstrapStateRead
+
+router = APIRouter(prefix="/bootstrap")
+
+
+@router.get("", response_model=BootstrapStateRead)
+def get_bootstrap_state() -> BootstrapStateRead:
+    return build_bootstrap_state(get_settings())
+
+
+@router.post("", response_model=BootstrapStateRead, status_code=status.HTTP_201_CREATED)
+def initialize_bootstrap(payload: BootstrapSetupPayload) -> BootstrapStateRead:
+    return persist_bootstrap_config(payload, get_settings())

server/src/app/api/v1/endpoints/employees.py

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+from __future__ import annotations
+
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from app.api.deps import get_db
+from app.schemas.employee import EmployeeCreate, EmployeeRead
+from app.services.employee import EmployeeService
+
+router = APIRouter()
+DbSession = Annotated[Session, Depends(get_db)]
+
+
+@router.get("", response_model=list[EmployeeRead])
+def list_employees(db: DbSession) -> list[EmployeeRead]:
+    return EmployeeService(db).list_employees()
+
+
+@router.post("", response_model=EmployeeRead, status_code=status.HTTP_201_CREATED)
+def create_employee(payload: EmployeeCreate, db: DbSession) -> EmployeeRead:
+    return EmployeeService(db).create_employee(payload)
+
+
+@router.get("/{employee_id}", response_model=EmployeeRead)
+def get_employee(employee_id: str, db: DbSession) -> EmployeeRead:
+    employee = EmployeeService(db).get_employee(employee_id)
+    if employee is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Employee not found")
+    return employee

server/src/app/api/v1/endpoints/health.py

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+from __future__ import annotations
+
+from fastapi import APIRouter
+from sqlalchemy import text
+
+from app.core.config import get_settings
+from app.db.session import get_engine
+
+router = APIRouter(prefix="/health")
+
+
+@router.get("")
+def health_check() -> dict[str, object]:
+    settings = get_settings()
+    database_ok = False
+    database_error = None
+
+    if settings.setup_completed:
+        try:
+            with get_engine().connect() as connection:
+                connection.execute(text("SELECT 1"))
+            database_ok = True
+        except Exception as exc:  # pragma: no cover - runtime connectivity branch
+            database_error = str(exc)
+
+    return {
+        "status": "ok" if database_ok else "degraded",
+        "database": {
+            "configured": settings.setup_completed,
+            "ok": database_ok,
+            "error": database_error,
+        },
+        "redis": {"configured": bool(settings.redis_url), "enabled": bool(settings.redis_url)},
+    }

server/src/app/api/v1/endpoints/reimbursements.py

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+from __future__ import annotations
+
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from app.api.deps import get_db
+from app.schemas.reimbursement import ReimbursementCreate, ReimbursementRead
+from app.services.reimbursement import ReimbursementService
+
+router = APIRouter()
+DbSession = Annotated[Session, Depends(get_db)]
+
+
+@router.get("", response_model=list[ReimbursementRead])
+def list_reimbursements(db: DbSession) -> list[ReimbursementRead]:
+    return ReimbursementService(db).list_reimbursements()
+
+
+@router.post("", response_model=ReimbursementRead, status_code=status.HTTP_201_CREATED)
+def create_reimbursement(payload: ReimbursementCreate, db: DbSession) -> ReimbursementRead:
+    return ReimbursementService(db).create_reimbursement(payload)
+
+
+@router.get("/{request_id}", response_model=ReimbursementRead)
+def get_reimbursement(request_id: str, db: DbSession) -> ReimbursementRead:
+    request = ReimbursementService(db).get_reimbursement(request_id)
+    if request is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Request not found")
+    return request

server/src/app/api/v1/router.py

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+from fastapi import APIRouter
+
+from app.api.v1.endpoints.bootstrap import router as bootstrap_router
+from app.api.v1.endpoints.employees import router as employees_router
+from app.api.v1.endpoints.health import router as health_router
+from app.api.v1.endpoints.reimbursements import router as reimbursements_router
+
+router = APIRouter()
+router.include_router(health_router, tags=["health"])
+router.include_router(bootstrap_router, tags=["bootstrap"])
+router.include_router(employees_router, prefix="/employees", tags=["employees"])
+router.include_router(reimbursements_router, prefix="/reimbursements", tags=["reimbursements"])