Add user password change functionality

Introduced a backend API endpoint for changing user passwords with validation. Added a new "User Settings" page in the frontend to allow users to update their passwords, including a matching UI update for navigation and styles.

backend/app/api/routes/me.py

@@ -1,7 +1,11 @@
-from fastapi import APIRouter, Depends
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.ext.asyncio import AsyncSession
+from app.core.db import get_db
 from app.core.deps import get_current_user
+from app.core.security import hash_password, verify_password
 from app.models.models import User
-from app.schemas.user import UserOut
+from app.schemas.user import UserOut, UserPasswordChange
+from app.services.audit import write_audit_log
 
 router = APIRouter()
 
@@ -9,3 +13,21 @@ router = APIRouter()
 @router.get("/me", response_model=UserOut)
 async def me(user: User = Depends(get_current_user)) -> UserOut:
     return UserOut.model_validate(user)
+
+
+@router.post("/me/password")
+async def change_password(
+    payload: UserPasswordChange,
+    user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+) -> dict:
+    if not verify_password(payload.current_password, user.password_hash):
+        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Current password is incorrect")
+
+    if verify_password(payload.new_password, user.password_hash):
+        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="New password must be different")
+
+    user.password_hash = hash_password(payload.new_password)
+    await db.commit()
+    await write_audit_log(db, action="auth.password_change", user_id=user.id, payload={})
+    return {"status": "ok"}