[UX] Add "Did you mean?" fuzzy suggestions for unknown columns/tables

### Is your feature request related to a problem? Please describe.
Currently, if a user makes a typo in a column or table name, DataFusion returns a strict "Not Found" error.

**Example:**
Given a table `users` with columns `["username", "email"]`:
```sql
SELECT usernme FROM users;

Start by tracing DataFusion's unknown-column and unknown-table error paths from the reported SQL example. The issue names no files, tests, matching algorithm, or acceptance criteria; done would require agreed fuzzy suggestions for both names and corresponding tests that verify the suggested wording.

Written by the indexing model from the issue text.