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/services/mail.py

@@ -0,0 +1,70 @@
+import smtplib
+from email.message import EmailMessage
+
+from sqlalchemy.orm import Session
+
+from app.core.config import get_settings
+from app.core.security import decrypt_secret, encrypt_secret
+from app.models.entities import MailSetting
+from app.schemas.common import MailSettingsIn, MailSettingsOut
+
+
+def get_mail_settings(db: Session) -> MailSetting:
+    settings = db.get(MailSetting, 1)
+    if not settings:
+        settings = MailSetting(id=1)
+        db.add(settings)
+        db.flush()
+    return settings
+
+
+def serialize_mail_settings(settings: MailSetting) -> MailSettingsOut:
+    return MailSettingsOut(
+        smtp_host=settings.smtp_host,
+        smtp_port=settings.smtp_port,
+        smtp_user=settings.smtp_user,
+        has_password=bool(settings.smtp_password_encrypted),
+        use_tls=settings.use_tls,
+        use_starttls=settings.use_starttls,
+        sender_address=settings.sender_address,
+        sender_name=settings.sender_name,
+    )
+
+
+def update_mail_settings(db: Session, payload: MailSettingsIn) -> MailSetting:
+    settings = get_mail_settings(db)
+    settings.smtp_host = payload.smtp_host
+    settings.smtp_port = payload.smtp_port
+    settings.smtp_user = payload.smtp_user
+    if payload.smtp_password is not None:
+        settings.smtp_password_encrypted = encrypt_secret(payload.smtp_password)
+    settings.use_tls = payload.use_tls
+    settings.use_starttls = payload.use_starttls
+    settings.sender_address = str(payload.sender_address) if payload.sender_address else None
+    settings.sender_name = payload.sender_name
+    return settings
+
+
+def send_mail(db: Session, to: str, subject: str, body: str) -> None:
+    settings = get_mail_settings(db)
+    if not settings.smtp_host or not settings.sender_address:
+        raise RuntimeError("SMTP is not configured")
+    message = EmailMessage()
+    message["From"] = f"{settings.sender_name} <{settings.sender_address}>"
+    message["To"] = to
+    message["Subject"] = subject
+    message.set_content(body)
+    password = decrypt_secret(settings.smtp_password_encrypted)
+    client_cls = smtplib.SMTP_SSL if settings.use_tls and not settings.use_starttls else smtplib.SMTP
+    with client_cls(settings.smtp_host, settings.smtp_port, timeout=20) as smtp:
+        if settings.use_starttls:
+            smtp.starttls()
+        if settings.smtp_user and password:
+            smtp.login(settings.smtp_user, password)
+        smtp.send_message(message)
+
+
+def invite_body(token: str) -> str:
+    link = f"{get_settings().instance_url.rstrip('/')}/accept-invite?token={token}"
+    return f"Welcome to NexaPantry.\n\nOpen this invitation link to set your password:\n{link}\n\nThe link expires automatically."
+