🔧 chore(repo): restructure project file hierarchy

- move project files out of fleetledger directory to root
- update .gitignore to reflect new .env path

📝 docs(README): add detailed project description

- provide an overview of FleetLedger's features and usage
- include setup instructions and security notes

app/auth.py

@@ -0,0 +1,75 @@
+from typing import Optional
+
+from fastapi import Depends, HTTPException, Request, status
+from passlib.context import CryptContext
+from sqlmodel import Session, select
+
+from .db import get_session
+from .models import User
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+
+def hash_password(password: str) -> str:
+    """Hash a password using bcrypt."""
+    return pwd_context.hash(password)
+
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    """Verify a password against a stored bcrypt hash."""
+    return pwd_context.verify(plain_password, hashed_password)
+
+
+def get_current_user(
+    request: Request,
+    session: Session = Depends(get_session),
+) -> Optional[User]:
+    """
+    Retrieve the currently logged-in user based on the session cookie.
+
+    Returns None if no user is logged in or the user is inactive.
+    """
+    user_id = request.session.get("user_id")
+    if not user_id:
+        return None
+    user = session.get(User, user_id)
+    if not user or not user.is_active:
+        # Clear session if the user was deactivated.
+        request.session.clear()
+        return None
+    return user
+
+
+def require_current_user(
+    current_user: Optional[User] = Depends(get_current_user),
+) -> User:
+    """
+    Require an authenticated user.
+
+    If not authenticated, redirect to /login with a 303 status.
+    """
+    if not current_user:
+        raise HTTPException(
+            status_code=status.HTTP_303_SEE_OTHER,
+            headers={"Location": "/login"},
+        )
+    return current_user
+
+
+def require_admin(
+    current_user: Optional[User] = Depends(get_current_user),
+) -> User:
+    """
+    Require an authenticated admin user.
+
+    Non-authenticated users are redirected to /login.
+    Non-admins receive HTTP 403.
+    """
+    if not current_user:
+        raise HTTPException(
+            status_code=status.HTTP_303_SEE_OTHER,
+            headers={"Location": "/login"},
+        )
+    if not current_user.is_admin:
+        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN)
+    return current_user