Add support for pg_stat_statements configuration in Targets

This commit introduces a `use_pg_stat_statements` flag for targets, allowing users to enable or disable the use of `pg_stat_statements` for query insights. It includes database schema changes, backend logic, and UI updates to manage this setting in both creation and editing workflows.

backend/app/api/routes/targets.py

@@ -64,6 +64,7 @@ async def create_target(
         username=payload.username,
         encrypted_password=encrypt_secret(payload.password),
         sslmode=payload.sslmode,
+        use_pg_stat_statements=payload.use_pg_stat_statements,
         tags=payload.tags,
     )
     db.add(target)
@@ -188,6 +189,11 @@ async def get_activity(target_id: int, user: User = Depends(get_current_user), d
 @router.get("/{target_id}/top-queries", response_model=list[QueryStatOut])
 async def get_top_queries(target_id: int, user: User = Depends(get_current_user), db: AsyncSession = Depends(get_db)) -> list[QueryStatOut]:
     _ = user
+    target = await db.scalar(select(Target).where(Target.id == target_id))
+    if not target:
+        raise HTTPException(status_code=404, detail="Target not found")
+    if not target.use_pg_stat_statements:
+        return []
     rows = (
         await db.scalars(
             select(QueryStat)