Add ruff linter/formatter for Python

- Add ruff as dev dependency
- Configure ruff in pyproject.toml with strict 88-char line limit
- Ignore B008 (FastAPI Depends pattern is standard)
- Allow longer lines in tests for readability
- Fix all lint issues in source files
- Add Makefile targets: lint-backend, format-backend, fix-backend

backend/routes/profile.py

@@ -1,15 +1,15 @@
 """Profile routes for user contact details."""
+
 from fastapi import APIRouter, Depends, HTTPException, status
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from auth import get_current_user
 from database import get_db
-from models import User, ROLE_REGULAR
+from models import ROLE_REGULAR, User
 from schemas import ProfileResponse, ProfileUpdate
 from validation import validate_profile_fields
 
-
 router = APIRouter(prefix="/api/profile", tags=["profile"])
 
 
@@ -29,9 +29,7 @@ async def get_godfather_email(db: AsyncSession, godfather_id: int | None) -> str
     """Get the email of a godfather user by ID."""
     if not godfather_id:
         return None
-    result = await db.execute(
-        select(User.email).where(User.id == godfather_id)
-    )
+    result = await db.execute(select(User.email).where(User.id == godfather_id))
     return result.scalar_one_or_none()