chore: initial project setup with backend, frontend, and infrastructure

Add complete NexaPantry application structure including:
- Docker Compose configuration with PostgreSQL, Redis, FastAPI backend, worker, frontend and Caddy
- Environment configuration template with database, auth, and service settings
- GitHub Actions CI workflow for backend/frontend linting, testing, auditing and Docker builds
- AGPL-3.0 license and comprehensive README with setup, development, and security documentation
- Backend

backend/app/api/routes/setup.py

@@ -0,0 +1,60 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy import select
+from sqlalchemy.orm import Session
+
+from app.core.security import hash_password
+from app.db.session import get_db
+from app.models.entities import AppSetting, Home, HomeMembership, HomeRole, InstanceRole, User
+from app.schemas.common import SetupCreate, SetupStatus, UserOut
+from app.services.audit import audit
+
+router = APIRouter()
+
+
+@router.get("/status", response_model=SetupStatus)
+def setup_status(db: Session = Depends(get_db)) -> SetupStatus:
+    admin_exists = db.scalar(select(User).where(User.instance_role == InstanceRole.ADMIN)) is not None
+    instance = db.get(AppSetting, "instance")
+    return SetupStatus(needs_setup=not admin_exists, instance=instance.value if instance else None)
+
+
+@router.post("/complete", response_model=UserOut, status_code=status.HTTP_201_CREATED)
+def complete_setup(payload: SetupCreate, db: Session = Depends(get_db)) -> User:
+    if db.scalar(select(User).where(User.instance_role == InstanceRole.ADMIN)):
+        raise HTTPException(status_code=409, detail="Instance already initialized")
+    user = User(
+        email=str(payload.email).lower(),
+        name=payload.name,
+        password_hash=hash_password(payload.password),
+        instance_role=InstanceRole.ADMIN,
+        language=payload.language,
+        theme=payload.theme,
+        timezone=payload.timezone,
+    )
+    home = Home(name=f"{payload.name}'s Home")
+    db.add_all(
+        [
+            user,
+            home,
+            AppSetting(
+                key="instance",
+                value={
+                    "name": payload.instance_name,
+                    "public_url": payload.public_url,
+                    "language": payload.language,
+                    "theme": payload.theme,
+                    "timezone": payload.timezone,
+                    "registration_enabled": False,
+                    "security": {"login_rate_limit": "10/minute"},
+                    "notifications": {"default_warning_days": 5},
+                },
+            ),
+        ]
+    )
+    db.flush()
+    db.add(HomeMembership(home_id=home.id, user_id=user.id, role=HomeRole.OWNER))
+    audit(db, user, "instance.setup", "user", user.id)
+    db.commit()
+    db.refresh(user)
+    return user
+